riscv: dts: sophgo: Add syscon node for cv18xx

riscv: dts: sophgo: Add syscon node for cv18xx

Add top syscon node and all subdevice nodes for cv18xx series SoC.

Co-developed-by: Inochi Amaoto <inochiama@gmail.com>
Signed-off-by: Longbin Li <looong.bin@gmail.com>
Tested-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
Link: https://lore.kernel.org/r/20251101014329.18439-3-looong.bin@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>