riscv: dts: sophgo: add sdcard support for milkv duo

Add sdhci dt node in SoC dtsi and enable it in milkv duo dts.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Reviewed-by: Inochi Amaoto <inochiama@outlook.com>
Link: https://lore.kernel.org/r/20240217144826.3944-1-jszhang@kernel.org


Signed-off-by: Inochi Amaoto <inochiama@outlook.com>
Signed-off-by: Chen Wang <unicorn_wang@outlook.com>