ARM64: dts: amlogic: add the ethernet TX delay configuration

This adds the amlogic,tx-delay-ns property with the old (hardcoded)
default value of 2ns to all boards which are using an RGMII ethernet
PHY.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Tested-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>
diff --git a/arch/arm64/boot/dts/amlogic/meson-gxl-s905d-p230.dts b/arch/arm64/boot/dts/amlogic/meson-gxl-s905d-p230.dts
index f66939c..7663d67 100644
--- a/arch/arm64/boot/dts/amlogic/meson-gxl-s905d-p230.dts
+++ b/arch/arm64/boot/dts/amlogic/meson-gxl-s905d-p230.dts
@@ -59,6 +59,8 @@
 	/* Select external PHY by default */
 	phy-handle = <&external_phy>;
 
+	amlogic,tx-delay-ns = <2>;
+
 	/* External PHY reset is shared with internal PHY Led signals */
 	snps,reset-gpio = <&gpio GPIOZ_14 0>;
 	snps,reset-delays-us = <0 10000 1000000>;