dt-bindings: serial: renesas: Document RZ/G2M v3.0 (r8a774a3) scif

Document scif bindings for the Renesas RZ/G2M v3.0 (a.k.a r8a774a3) SoC.

Signed-off-by: Oliver Rhodes <oliver.rhodes.aj@renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20240725100534.5374-6-oliver.rhodes.aj@renesas.com


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