boards: renesas: Add minimal support for board RZ/G3S-SMARC

This adds minimal support for board RZ/G3S-SMARC

Signed-off-by: Nhut Nguyen <nhut.nguyen.kc@renesas.com>
Signed-off-by: Tien Nguyen <tien.nguyen.zg@renesas.com>
Signed-off-by: Binh Nguyen <binh.nguyen.xw@renesas.com>