dt-bindings: serial: renesas,scif: Document r8a779h0 bindings

R-Car V4M (R8A779H0) SoC has the R-Car Gen4 compatible SCIF ports, so
document the SoC specific bindings.

Signed-off-by: Nghia Nguyen <nghia.nguyen.jg@renesas.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/49b854603c2c3ed6b2edd441f1d55160e0453b70.1709741175.git.geert+renesas@glider.be


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>