dt-bindings: can: rcar_can: Add r8a7742 support

Document RZ/G1H (r8a7742) SoC specific bindings. The R8A7742 CAN module
is identical to R-Car Gen2 family.

No driver change is needed due to the fallback compatible value
"renesas,rcar-gen2-can".

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Chris Paterson <Chris.Paterson2@renesas.com>
Link: https://lore.kernel.org/r/20200816190732.6905-3-prabhakar.mahadev-lad.rj@bp.renesas.com
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

Documentation/devicetree/bindings/net/can/rcar_can.txt

@@ -2,7 +2,8 @@ Renesas R-Car CAN controller Device Tree Bindings
 -------------------------------------------------
 
 Required properties:
-- compatible: "renesas,can-r8a7743" if CAN controller is a part of R8A7743 SoC.
+- compatible: "renesas,can-r8a7742" if CAN controller is a part of R8A7742 SoC.
+	      "renesas,can-r8a7743" if CAN controller is a part of R8A7743 SoC.
 	      "renesas,can-r8a7744" if CAN controller is a part of R8A7744 SoC.
 	      "renesas,can-r8a7745" if CAN controller is a part of R8A7745 SoC.
 	      "renesas,can-r8a77470" if CAN controller is a part of R8A77470 SoC.