dt-bindings: serial: renesas,hscif: Document r8a7742 bindings

RZ/G1H (R8A7742) SoC also has the R-Car gen2 compatible HSCIF ports,
so document the SoC specific bindings.
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Marian-Cristian Rotariu <marian-cristian.rotariu.rb@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Rob Herring <robh@kernel.org>

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

@@ -24,6 +24,7 @@ properties:
 
       - items:
           - enum:
+              - renesas,hscif-r8a7742      # RZ/G1H
               - renesas,hscif-r8a7743      # RZ/G1M
               - renesas,hscif-r8a7744      # RZ/G1N
               - renesas,hscif-r8a7745      # RZ/G1E