boards: renesas: Add minimal support for board RZ/A3UL-SMARC

This adds minimal support for board RZ/A3UL-SMARC

Signed-off-by: Nhut Nguyen <nhut.nguyen.kc@renesas.com>
Signed-off-by: Phuc Pham <phuc.pham.xr@bp.renesas.com>
Signed-off-by: Tien Nguyen <tien.nguyen.zg@renesas.com>