ARM: dts: armada-370-xp: Fixup mdio DT warning

MDIO has a reg property so the unit name should contain an address.
Take the opportunity to use the node label instead of the full name.

Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>

arch/arm/boot/dts/armada-xp-axpwifiap.dts

@@ -111,16 +111,6 @@
 				status = "okay";
 			};
 
-			mdio {
-				phy0: ethernet-phy@0 {
-					reg = <0>;
-				};
-
-				phy1: ethernet-phy@1 {
-					reg = <1>;
-				};
-			};
-
 			ethernet@70000 {
 				pinctrl-0 = <&ge0_rgmii_pins>;
 				pinctrl-names = "default";
@@ -153,6 +143,16 @@
 	};
 };
 
+&mdio {
+	phy0: ethernet-phy@0 {
+		reg = <0>;
+	};
+
+	phy1: ethernet-phy@1 {
+		reg = <1>;
+	};
+};
+
 &pinctrl {
 	pinctrl-0 = <&phy_int_pin>;
 	pinctrl-names = "default";