dt-bindings: memory: renesas,rpc-if: Document R-Car V4H support

dt-bindings: memory: renesas,rpc-if: Document R-Car V4H support

Document support for the SPI Multi I/O Bus Controller (RPC-IF) in the
R-Car V4H SoC.

Signed-off-by: Hai Pham <hai.pham.ud@renesas.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/c268cb4497cbe79773bb6568f36c37adc6fb5bbe.1665582645.git.geert+renesas@glider.be
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>