riscv: dts: sophgo: add initial CV1800B SoC device tree

Add initial device tree for the CV1800B RISC-V SoC by SOPHGO.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Acked-by: Chen Wang <unicorn_wang@outlook.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>