ath79: ar7240: Update dts for current ag71xx driver

Signed-off-by: Chuanhong Guo <gch981213@gmail.com>

target/linux/ath79/dts/ar7240.dtsi

@@ -33,7 +33,25 @@
 };
 
 &mdio0 {
+	status = "okay";
+
+	compatible = "qca,ar7240-mdio";
 	builtin-switch;
+
+	builtin_switch: switch0@1f {
+		compatible = "qca,ar8216-builtin";
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		reg = <0x1f>;
+
+		mdio-bus {
+			swphy4: ethernet-phy@4 {
+				reg = <4>;
+				phy-mode = "mii";
+			};
+		};
+	};
 };
 
 &eth0 {
@@ -43,10 +61,8 @@
 
 	resets = <&rst 8>, <&rst 9>;
 	reset-names = "phy", "mac";
-};
-
-&mdio1 {
-	builtin-switch;
+	phy-mode = "mii";
+	phy-handle = <&swphy4>;
 };
 
 &eth1 {