dt-bindings: riscv: add Sophgo SG2042_EVB_V1.X/V2.0 bindings

dt-bindings: riscv: add Sophgo SG2042_EVB_V1.X/V2.0 bindings

Add DT binding documentation for the Sophgo SG2042_EVB_V1.X/V2.0 board [1].

Link: https://github.com/sophgo/sophgo-hardware/tree/master/SG2042/SG2042-x8-EVB
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Han Gao <rabenda.cn@gmail.com>
Reviewed-by: Nutty Liu <liujingqi@lanxincomputing.com>
Reviewed-by: Chen Wang <unicorn_wang@outlook.com>
Link: https://lore.kernel.org/r/204c8214aa084d592e8dc45d6c5ca23381937b54.1751700954.git.rabenda.cn@gmail.com
Signed-off-by: Inochi Amaoto <inochiama@gmail.com>
Signed-off-by: Chen Wang <unicorn_wang@outlook.com>
Signed-off-by: Chen Wang <wangchen20@iscas.ac.cn>