PlutoSDR: Prepare for v0.28 release

0b21f8d .gitmodules: Switch submod linux to 2018_R1 release branch
fe5dc06 Makefile: Auto-generate LICENSE file
bd13416 Makefile: Allow firmware builds without Xilinx Vivado installed
bb50331 Makefile: New target legal-info

Submodule linux f457f60..b07f3c6:
  > drivers: iio: frequency: cf_axi_dds: Fix driver remove path
  > drivers: iio: frequency: cf_axi_dds: Fix function return path
  > iio: adc: ad9361: use proper MAX_BASEBAND_RATE define
  > iio: adc: ad9361: Validate MAX Half Band filter rates
  > clk: altera-a10-fpll: Fix calibration for phase aligned mode
  > adp5061: Add support for termination current property
  > adp5061: Add support for reading the battery status
  > adp5061: Add support for reading the charger status
  > adp5061: Add support for charging voltage limit enable
  > adp5061: Add support for battery charging enable
  > iio: adc: ad9361: Fix Tx Mon Delay Counter setting
  > iio: adc: ad9361: Disable CP offset current, clear 0x23D[D4] 0x27D[D4]
  > configs: zynq_xcomm_adv7511_defconfig: Enable ADP5061 driver
  > adp5061: Add devicetree support for adp5061
  > adp5061: New driver for ADP5061 I2C battery charger
  > Documentation: dt-bindings: add adi,adp5061 docs
  > power: supply: core: Add power_supply_prop_precharge
  > microblaze: dts: Add a link to dt-bindings
  > microblaze: dts: kcu105_fmcdaq2: Use the base design dtsi
  > microblaze: dts: Add FMCOMMS4 support for KCU105
  > microblaze: dts: Add FMCOMMS2-3 support for KCU105
  > microblaze: dts: Add a dtsi for the KCU105 base design
  > microblaze: dts: Fix the dtc warnings
  > .travis.yml: add ZynqMP to the build run
  > iio: adc: ad9361: Add option to set Reg Gain Step Config2 0x106 [D6:D4]
  > dts: vc707_fmcjesdadc1: Update to ADI JESD204 link-layer peripherals
  > dts: kc705_fmcjesdadc1: Update to ADI JESD204 link-layer peripherals
  > dts: vc707_fmcdaq2: Update to ADI JESD204 link-layer peripherals
  > dts: kc705_fmcdaq2: Update to ADI JESD204 link-layer peripherals
  > Documentation: dt-bindings: add adi,jesd204 tx/rx docs
  > .travis.yml: check last commit if no pull-request
  > iio: altera_adxcvr: Support more than 4 lanes
  > iio: adc: ad9361: Fix the formula for computing the AuxDAC word
  > iio: adc: ad9361: Fix typo in AGC Attack Delay computation
  > .travis.yml: use TRAVIS_BRANCH env var during pull request
  > iio: adc: ad9361: add ad9361_write_bist_reg() accessor to cache bist reg value
  > arch: arm: sidekiqz2: isolate on-board i2c to host SMBus
  > arch: arm: sidekiqz2: add reset GPIO to device-tree
  > arch: arm: sidekiqz2: enable support for `ti,tca6408` chip
  > Merge pull request #61 from analogdevicesinc/travis-ci-test
  > drivers/iio/logic/m2k-trigger-ad: Add AXI ADC trigger driver
  > drivers/iio/frequency/cf_axi_dds: Add support for m2k AD9963
  > iio: ad_adc: Add M2K ADC support
  > drivers/iio/logic/m2k-fabric: Enable USR power by default
  > iio: Add m2k-fabric driver
  > iio: Add preliminary ad9963 driver
  > iio: Add m2k logic analyzer
  > clk: Add ADF4360 driver support
  > iio: Track enabled channels on a per channel basis
  > iio: Move scan mask management to the core
  > iio: Don't initialize buffer->scan_mask in drivers
  > iio: Allow channels to share storage elements
  > iio: Add macro to declare share enum "available" attributes
  > iio: adc: ad9361: add short-hand var `new_rate` in clk notifier funcs
  > iio: adc: ad9361: fix arguments for ad9361_phy_parse_dt() when not using DT
  > iio: adc: ad9361: clamp the user entered RF BW between min/max
  > iio: adc: ad9361: Add comment explaining the origin of three magic values
  > iio: adc: ad9361: Add comment explaining the origin of three magic values
  > iio: adc: ad9361: move AuxDAC initialization earlier in the setup
  > iio: adc: ad9361: move GPO initialization earlier in the setup
  > iio: Fix IIO_VAL_FRACTIONAL_LOG2 newline termination
  > drivers: mtd: spi-nor: add support for ISSI IS25WP256D flash
  > drivers: mtd: spi-nor: remove USE_FSR capability for is25lp256d flash
  > zynq-sidekiqz2-reva.dts: enable on-board ref oscillator via GPO2 bit
  > zynq-sidekiqz2-reva.dts: remove adm1177 definition
  > arch: arm: add base support for Sidekiq Z2 board
  > Merge pull request #38 from analogdevicesinc/openwrt_compat_stuff
  > iio: adis_lib: Initialize trigger before requesting interrupt
  > configs: zynq_xcomm_adv7511_defconfig: Add USB configfs ACM support
  > iio: adc: ad9371: Fix loadable gain table support
  > Merge branch 'master' of https://github.com/analogdevicesinc/linux
  > iio: frequency: ad9162: Add support complex (IQ channel) mode
  > dts: zynq-zc706-adv7511-fmcomms11: Add Support for RevB hardware.
  > iio: frequency: ad9162: Cleanup no functional changes
  > iio: frequency: ad9162: Add support for setting the JESD204 Lane Rate
  > iio: frequency: ad9162: Make SYSREF optional to support JESD204 Subclass 0
  > iio: adc: ad9467: AD9625 add support for setting the JESD204 Lane Rate
  > iio: jesd204: axi_jesd204_[rx|tx]: Add support for JESD204 Subclass 0
  > dts: zynq-zc706-adv7511-adrv9371.dts: Fix name - avoid warning
  > dts: adi-adrv9371.dtsi: Remove orphan fixed-clock

Submodule buildroot 79ccad2..45f8f2b:
  > board/m2k/genimage-msd.cfg: Use auto-generated License file
  > board/m2k/msd/.gitignore: Add ignore for autogenerated LICENSE file
  > board/pluto/busybox-1.25.0.config: Update config for busybox-1.27.2
  > Merge remote-tracking branch 'mainline/2018.02.x' into test-update

Submodule hdl bf3ba44..944edeb:
  > axi_logic_analyzer: Fix push-pull/open-drain selection