dt-bindings: mmc: renesas,sdhi: Document R-Car V4H support

Document support for the SD Card/MMC Interface on the Renesas R-Car V4H
(R8A779G0) SoC.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/7ee7fdb6a46fc9f0e50c2b803ede6b4b2fdfa450.1665558324.git.geert+renesas@glider.be


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