ARM: dts: sunxi: Add missing mdio label

This patch add missing mdio label for sun[457]i.
Signed-off-by: Aleksei Mamlin <mamlinav@gmail.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

arch/arm/boot/dts/sun4i-a10.dtsi

@@ -465,7 +465,7 @@ emac: ethernet@01c0b000 {
 			status = "disabled";
 		};
 
-		mdio@01c0b080 {
+		mdio: mdio@01c0b080 {
 			compatible = "allwinner,sun4i-a10-mdio";
 			reg = <0x01c0b080 0x14>;
 			status = "disabled";

arch/arm/boot/dts/sun5i-a10s.dtsi

@@ -361,7 +361,7 @@ emac: ethernet@01c0b000 {
 			status = "disabled";
 		};
 
-		mdio@01c0b080 {
+		mdio: mdio@01c0b080 {
 			compatible = "allwinner,sun4i-a10-mdio";
 			reg = <0x01c0b080 0x14>;
 			status = "disabled";

arch/arm/boot/dts/sun7i-a20.dtsi

@@ -580,7 +580,7 @@ emac: ethernet@01c0b000 {
 			status = "disabled";
 		};
 
-		mdio@01c0b080 {
+		mdio: mdio@01c0b080 {
 			compatible = "allwinner,sun4i-a10-mdio";
 			reg = <0x01c0b080 0x14>;
 			status = "disabled";