dt-bindings: net: renesas, ravb: Add support for r8a7742 SoC

Document RZ/G1H (R8A7742) SoC 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: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/net/renesas,ravb.txt

@@ -5,6 +5,7 @@ interface contains.
 
 Required properties:
 - compatible: Must contain one or more of the following:
+      - "renesas,etheravb-r8a7742" for the R8A7742 SoC.
       - "renesas,etheravb-r8a7743" for the R8A7743 SoC.
       - "renesas,etheravb-r8a7744" for the R8A7744 SoC.
       - "renesas,etheravb-r8a7745" for the R8A7745 SoC.