Add DT support to driver and add to .dtsi file.
Setup pins and spidev in .dts file.
SPI is disabled by default.

Signed-off-by: Noralf Tronnes <notro@tronnes.org>

BCM2708: don't register SPI controller when using DT

The device for the SPI controller is in the Device Tree.
Only register the device when not using DT.

Signed-off-by: Noralf Tronnes <notro@tronnes.org>

spi: bcm2835: make driver available on ARCH_BCM2708

Make this driver available on ARCH_BCM2708

Signed-off-by: Noralf Tronnes <notro@tronnes.org>

bcm2708: Remove the prohibition on mixing SPIDEV and DT