arm64: dts: imx8mn-evk: Remove invalid Atheros properties

None of these at803x properties are documented anywhere, so just
remove them.
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mn-evk.dtsi

@@ -49,9 +49,6 @@ mdio {
 		ethphy0: ethernet-phy@0 {
 			compatible = "ethernet-phy-ieee802.3-c22";
 			reg = <0>;
-			at803x,led-act-blind-workaround;
-			at803x,eee-disabled;
-			at803x,vddio-1p8v;
 		};
 	};
 };