riscv: dts: sophgo: add Huashan Pi board device tree

riscv: dts: sophgo: add Huashan Pi board device tree

Add initial device tree files for the Huashan Pi board.

Note: The boot of CV1812H chip needs a rtos firmware for coprocessor to
function properly. To make the soc happy, reserved the last 2M memory
for the rtos firmware.

Signed-off-by: Inochi Amaoto <inochiama@outlook.com>
Link: https://en.sophgo.com/product/introduce/huashan.html
Link: https://en.sophgo.com/product/introduce/cv181xH.html
Link: https://github.com/milkv-duo/duo-buildroot-sdk/blob/develop/build/boards/cv181x/cv1812h_wevb_0007a_emmc_huashan/memmap.py#L15
Reviewed-by: Jisheng Zhang <jszhang@kernel.org>
Acked-by: Chen Wang <unicorn_wang@outlook.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>