dt-bindings: phy: rcar-gen2: Add r8a7742 support

Add USB PHY support for r8a7742 SoC. Renesas RZ/G1H (R8A7742)
USB PHY is identical to the R-Car Gen2 family.
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/phy/rcar-gen2-phy.txt

@@ -4,7 +4,8 @@ This file provides information on what the device node for the R-Car generation
 2 USB PHY contains.
 
 Required properties:
-- compatible: "renesas,usb-phy-r8a7743" if the device is a part of R8A7743 SoC.
+- compatible: "renesas,usb-phy-r8a7742" if the device is a part of R8A7742 SoC.
+	      "renesas,usb-phy-r8a7743" if the device is a part of R8A7743 SoC.
 	      "renesas,usb-phy-r8a7744" if the device is a part of R8A7744 SoC.
 	      "renesas,usb-phy-r8a7745" if the device is a part of R8A7745 SoC.
 	      "renesas,usb-phy-r8a77470" if the device is a part of R8A77470 SoC.