dt-bindings: mmc: renesas,sdhi: Document RZ/V2H(P) support

dt-bindings: mmc: renesas,sdhi: Document RZ/V2H(P) support

The SD/MMC block on the RZ/V2H(P) ("R9A09G057") SoC is similar to that
of the R-Car Gen3, but it has some differences:
- HS400 is not supported.
- It has additional SD_STATUS register to control voltage,
  power enable and reset.
- It supports fixed address mode.

To accommodate these differences, a SoC-specific 'renesas,sdhi-r9a09g057'
compatible string is added.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20240724182119.652080-2-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>