dt-bindings: dmaengine: usb-dmac: Add binding for r8a774a1

This patch adds binding for r8a774a1 (RZ/G2M).

Signed-off-by: Biju Das <biju.das@bp.renesas.com>
Reviewed-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Documentation/devicetree/bindings/dma/renesas,usb-dmac.txt

@@ -7,6 +7,7 @@ Required Properties:
 	  - "renesas,r8a7744-usb-dmac" (RZ/G1N)
 	  - "renesas,r8a7745-usb-dmac" (RZ/G1E)
 	  - "renesas,r8a77470-usb-dmac" (RZ/G1C)
+	  - "renesas,r8a774a1-usb-dmac" (RZ/G2M)
 	  - "renesas,r8a7790-usb-dmac" (R-Car H2)
 	  - "renesas,r8a7791-usb-dmac" (R-Car M2-W)
 	  - "renesas,r8a7793-usb-dmac" (R-Car M2-N)