Only tested with SBI and supervisor mode, but that's all I have now.
Add checked in copies of the device tree needed for a uboot uimage
needed to start it.
Most of changes were moving around where macros were defined, plus the
following:
- Remove requirement for floating point on RV64 to support booting
monitor core on U54 SoC.
- Add support for Debug LEDs on HiFive Unleashed Board