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

The R-Car V4M (R8A779H0) SoC has R-Car Gen4 compatible HSCIF 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>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/55b458e0ba9824e1246e556075bf882032c37279.1706095578.git.geert@linux-m68k.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/serial/renesas,hscif.yaml

@@ -59,6 +59,7 @@ properties:
               - renesas,hscif-r8a779a0     # R-Car V3U
               - renesas,hscif-r8a779f0     # R-Car S4-8
               - renesas,hscif-r8a779g0     # R-Car V4H
+              - renesas,hscif-r8a779h0     # R-Car V4M
           - const: renesas,rcar-gen4-hscif # R-Car Gen4
           - const: renesas,hscif           # generic HSCIF compatible UART