The DTS compilation was arm platforms only. Moving it to the top level
config file, making it available to RISCV platforms. The generated files
are almost identical with minor differences. A new argument(--arch) is
added to the hardware_gen.py for the differences.
Move DTS to the kernel in preparation for using them to autogenerate
hardware headers.
This includes DTS that we didn't have previously, extracted from the
Linux kernel. Everything except TX2 comes from Linux v4.20, extracted
with the following commands:
checkout https://github.com/torvalds/linux.git v4.20
./update-dts.sh /path/to/linux/checkout
The TX2 dts is identical to the one that was found in seL4_tools.
