dt-bindings: soc: renesas: Document Renesas RZ/G3S SoC variants

Document RZ/G3S (R9A08G045) SoC variants.

Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20230912045157.177966-3-claudiu.beznea.uj@bp.renesas.com


Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>