dt-bindings: soc: renesas: Document RZ/G3S SMARC SoM

dt-bindings: soc: renesas: Document RZ/G3S SMARC SoM

Document the Renesas RZ/G3S SMARC SoM board which is based on the
Renesas RZ/G3S (R9A08G045S33) SoC.

Suggested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20230929053915.1530607-24-claudiu.beznea@bp.renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>