ASoC: dt-bindings: renesas,rz-ssi: Document the Renesas RZ/G3S SoC

The SSI IP variant present on the Renesas RZ/G3S SoC is similar to the
one found on the Renesas RZ/G2{UL, L, LC} SoCs. Add documentation for
it.

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://patch.msgid.link/20241210170953.2936724-20-claudiu.beznea.uj@bp.renesas.com


Signed-off-by: Mark Brown <broonie@kernel.org>