arm64: dts: renesas: condor: add EtherAVB support

Define the Condor board dependent part of the EtherAVB device node.

Based  on the original (and large) patch by Vladimir Barinov.
Signed-off-by: NVladimir Barinov <vladimir.barinov@cogentembedded.com>
Signed-off-by: NSergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: NSimon Horman <horms+renesas@verge.net.au>

arch/arm64/boot/dts/renesas/r8a77980-condor.dts

@@ -15,6 +15,7 @@
 
 	aliases {
 		serial0 = &scif0;
+		ethernet0 = &avb;
 	};
 
 	chosen {
@@ -28,6 +29,18 @@
 	};
 };
 
+&avb {
+	phy-mode = "rgmii-id";
+	phy-handle = <&phy0>;
+	renesas,no-ether-link;
+	status = "okay";
+
+	phy0: ethernet-phy@0 {
+		rxc-skew-ps = <1500>;
+		reg = <0>;
+	};
+};
+
 &extal_clk {
 	clock-frequency = <16666666>;
 };