dt-bindings: mmc: renesas,sdhi: Document RZ/T2H and RZ/N2H support

Add SDHI bindings for the Renesas RZ/T2H (a.k.a R9A09G077) and RZ/N2H
(a.k.a R9A09G087) SoCs. Use `renesas,sdhi-r9a09g057` as a fallback since
the SD/MMC block on these SoCs is identical to the one on RZ/V2H(P),
allowing reuse of the existing driver without modifications.

Update the binding schema to reflect differences: unlike RZ/V2H(P),
RZ/T2H and RZ/N2H do not require the `resets` property and use only a
two clocks instead of four.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20250617164914.158091-1-prabhakar.mahadev-lad.rj@bp.renesas.com


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>