arm64: dts: renesas: r8a77980: add GEther support

Define the generic R8A77980 part of the GEther device node.

Based on the original (and large) patch by Vladimir Barinov.
Signed-off-by: Vladimir Barinov <vladimir.barinov@cogentembedded.com>
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
[simon: add resets property]
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm64/boot/dts/renesas/r8a77980.dtsi

@@ -417,6 +417,18 @@ GIC_SPI 367 IRQ_TYPE_LEVEL_HIGH
 			dma-channels = <16>;
 		};
 
+		gether: ethernet@e7400000 {
+			compatible = "renesas,gether-r8a77980";
+			reg = <0 0xe7400000 0 0x1000>;
+			interrupts = <GIC_SPI 21 IRQ_TYPE_LEVEL_HIGH>;
+			clocks = <&cpg CPG_MOD 813>;
+			power-domains = <&sysc R8A77980_PD_ALWAYS_ON>;
+			resets = <&cpg 813>;
+			#address-cells = <1>;
+			#size-cells = <0>;
+			status = "disabled";
+		};
+
 		mmc0: mmc@ee140000 {
 			compatible = "renesas,sdhi-r8a77980",
 				     "renesas,rcar-gen3-sdhi";