boards: nxp: imx8mp: Fix unit and first address mismatch

This fixes the following warning:

> devicetree error: unit address and first address in 'reg' (0x1) don't
> match for /soc/enet@30be0000/mdio/phy@0

Signed-off-by: Reto Schneider <[email protected]>

Author: rettichschnidi

boards/nxp/imx8mp_evk/imx8mp_evk_mimx8ml8_a53.dts

@@ -54,7 +54,7 @@
 	pinctrl-0 = <&pinmux_mdio>;
 	pinctrl-names = "default";
 	status = "okay";
-	phy: phy@0 {
+	phy: phy@1 {
 		compatible = "realtek,rtl8211f";
 		reg = <1>;
 		status = "okay";