arm64: renesas: r8a7795: Add dummy dma-controller nodes

Add dummy nodes for the 3 DMA controllers.
This allows to start describing DMA channels for DMA slaves now.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm64/boot/dts/renesas/r8a7795.dtsi

@@ -79,5 +79,17 @@
 			#clock-cells = <2>;
 			#power-domain-cells = <0>;
 		};
+
+		dmac0: dma-controller@e6700000 {
+			/* Empty node for now */
+		};
+
+		dmac1: dma-controller@e7300000 {
+			/* Empty node for now */
+		};
+
+		dmac2: dma-controller@e7310000 {
+			/* Empty node for now */
+		};
 	};
 };