arch: arm: agilex: Clean up DT settings in U-Boot dtsi files

arch: arm: agilex: Clean up DT settings in U-Boot dtsi files

Reorganize misplaced properties by moving board-common settings from
socfpga_agilex_socdk-u-boot.dtsi to socfpga_agilex-u-boot.dtsi to maintain
proper separation between common and board-level configurations.

Signed-off-by: Tingting Meng <tingting.meng@altera.com>
Signed-off-by: Alif Zakuan Yuslaimi <alif.zakuan.yuslaimi@altera.com>
Reviewed-by: Tien Fong Chee <tien.fong.chee@altera.com>