arm64: dts: ti: k3-am65-mcu: add phy-gmii-sel node

Add DT node for the TI AM65x SoC phy-gmii-sel PHY required for Ethernet
ports mode selection.
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>

arch/arm64/boot/dts/ti/k3-am65-mcu.dtsi

@@ -12,6 +12,12 @@ mcu_conf: scm_conf@40f00000 {
 		#address-cells = <1>;
 		#size-cells = <1>;
 		ranges = <0x0 0x0 0x40f00000 0x20000>;
+
+		phy_gmii_sel: phy@4040 {
+			compatible = "ti,am654-phy-gmii-sel";
+			reg = <0x4040 0x4>;
+			#phy-cells = <1>;
+		};
 	};
 
 	mcu_uart0: serial@40a00000 {