boards stm32h747i_disco: Add missing mdio node

Akin to the changes in
ab29ee5
Add missing mdio node for
stm32h747i_disco/stm32h747i_disco_stm32h747xx_m7

Without this, samples/net/sockets/echo_server
fails to build in this board.

Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>

boards/st/stm32h747i_disco/stm32h747i_disco_stm32h747xx_m7.dts

@@ -130,9 +130,7 @@
 	 */
 	status = "okay";
 	pinctrl-0 = <&eth_ref_clk_pa1
-		     &eth_mdio_pa2
 		     &eth_crs_dv_pa7
-		     &eth_mdc_pc1
 		     &eth_rxd0_pc4
 		     &eth_rxd1_pc5
 		     &eth_tx_en_pg11
@@ -141,6 +139,18 @@
 	pinctrl-names = "default";
 };
 
+&mdio {
+	status = "okay";
+	pinctrl-0 = <&eth_mdio_pa2 &eth_mdc_pc1>;
+	pinctrl-names = "default";
+
+	ethernet-phy@0 {
+		compatible = "ethernet-phy";
+		reg = <0x00>;
+		status = "okay";
+	};
+};
+
 &rng {
 	status = "okay";
 };