imx8m{m,n}-venice-gw7902: add support for GPY111 phy

The TI DP83867 phy has been replaced with the MaxLinear GPY111 phy
due to part availability. Add support for it:
 - increase post-reset time to 300ms per datasheet
 - add tx-delay/rx-delay config

Signed-off-by: Tim Harvey <tharvey@gateworks.com>
diff --git a/arch/arm/dts/imx8mm-venice-gw7902-u-boot.dtsi b/arch/arm/dts/imx8mm-venice-gw7902-u-boot.dtsi
index 1e1769f..f21e46b 100644
--- a/arch/arm/dts/imx8mm-venice-gw7902-u-boot.dtsi
+++ b/arch/arm/dts/imx8mm-venice-gw7902-u-boot.dtsi
@@ -158,7 +158,7 @@
 &fec1 {
 	phy-reset-gpios = <&gpio1 10 GPIO_ACTIVE_LOW>;
 	phy-reset-duration = <1>;
-	phy-reset-post-delay = <1>;
+	phy-reset-post-delay = <300>;
 };
 
 &pinctrl_fec1 {