arm64: dts: imx8mm-kontron: Fix reset delays for ethernet PHY

According to the datasheet the VSC8531 PHY expects a reset pulse of 100 ns
and a delay of 15 ms after the reset has been deasserted. Set the matching
values in the devicetree.
Reported-by: Heiko Thiery <heiko.thiery@gmail.com>
Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-s.dts

@@ -121,8 +121,8 @@ mdio {
 
 		ethphy: ethernet-phy@0 {
 			reg = <0>;
-			reset-assert-us = <100>;
-			reset-deassert-us = <100>;
+			reset-assert-us = <1>;
+			reset-deassert-us = <15000>;
 			reset-gpios = <&gpio4 27 GPIO_ACTIVE_LOW>;
 		};
 	};