arm64: dts: imx8mp-evk: disable CLKOUT clock for ENET PHY

According to commit 0a4355c2 ("net: phy: realtek: add dt property to
disable CLKOUT clock"), diable CLKOUT clock for FEC PHY to save power on
i.MX8MP EVK board.
Signed-off-by: Joakim Zhang <qiangqing.zhang@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mp-evk.dts

@@ -100,6 +100,7 @@ ethphy0: ethernet-phy@1 {
 			reset-gpios = <&gpio4 22 GPIO_ACTIVE_LOW>;
 			reset-assert-us = <10000>;
 			reset-deassert-us = <80000>;
+			realtek,clkout-disable;
 		};
 	};
 };
@@ -123,6 +124,7 @@ ethphy1: ethernet-phy@1 {
 			reset-gpios = <&gpio4 2 GPIO_ACTIVE_LOW>;
 			reset-assert-us = <10000>;
 			reset-deassert-us = <80000>;
+			realtek,clkout-disable;
 		};
 	};
 };