Adds device-tree, DEMB board file, mach-hibvt entry, and ARCH_HI3516CV100
Kconfig for the Hi3516CV100 SoC family (V1 generation, ARM926EJ-S /
ARMv5TE, the parent of the Hi3516CV200 family already supported in
upstream-patches).

cv100 is architecturally a strict subset of cv200 — same single
ARM926EJ-S core, same SP804 dual-timers, same PL011 UARTs and PL022
SPI controllers, same hisi-femac ethernet, same FMC flash controller,
same pinctrl-single pinmux block, all at identical MMIO addresses.
The relevant difference for kernel boot is the VIC base — 0x10140000
on cv100 vs 0x100d0000 on cv200 — which is overridden in the cv100
dtsi via a label-based reference (&vic), reusing cv200's full DT
scaffold via #include "hi3516cv200.dtsi".

The CRG driver (drivers/clk/hisilicon/clk-hi3516cv200.c) handles
cv100 unchanged — cv100's CRG register layout is a strict subset
of cv200's (cv200 added a handful of extra clock gates for new
peripherals that cv100 doesn't have). ARCH_HI3516CV100 just
`select COMMON_CLK_HI3516CV200` and the existing
"hisilicon,hi3518ev20x-clock" compatible matches both SoCs.

The mach-hibvt entry reuses mach-hi3518ev20x.c (the cv200 mach file)
verbatim, just adding "hisilicon,hi3516cv100" to its dt_compat array
and the cv100 IO header to mach/io.h. HI_ZRELADDR is 0x80008000
(same as the rest of the V1/V2 ARMv5TE family).

Sibling V1 SoCs (die-identical per qemu-hisilicon machine model
decoding) can attach to this dtsi as overlays: Hi3518AV100,
Hi3518CV100, Hi3518EV100.

cv100's V1 single-controller register-poll i2c hardware is not
driver-compatible with cv200's HiBVT i2c — the inherited i2c_bus0/1/2
DT nodes are explicitly marked disabled in hi3516cv100.dtsi. Boot
does not depend on them; userspace can drive the sensor i2c MMIO
directly via a separate kernel module if needed.

Tested under qemu-system-arm -M hi3516cv100 with the OpenIPC userspace:
- Boots to login prompt cleanly, no Oops/panic/BUG
- hisi-femac eth0 link UP at 100Mbps/Full, DHCP from SLIRP
  obtains 10.0.2.15, ICMP echo to gateway 10.0.2.2 succeeds (~17ms)