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

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