arm64: dts: sprd: Add support for Unisoc's UMS9620

Add basic support for Unisoc's UMS9620, with this patch,
the board ums9620-2h10 can run into console.

Link: https://lore.kernel.org/r/20231218100234.1102916-4-chunyan.zhang@unisoc.com
Signed-off-by: Chunyan Zhang <chunyan.zhang@unisoc.com>