arm64: dts: m3ulcb: Fix EthernetAVB PHY timing

Set PHY rxc-skew-ps to 1500 and all other values to their default values.

This is intended to to address failures in the case of 1Gbps communication
using the salvator-x board with the KSZ9031RNX phy. This has been
reported to occur with both the r8a7795 (H3) and r8a7796 (M3-W) SoCs.

Based in a similar patch for the r8a7796 salvator-x by Kazuya Mizuguchi.
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm64/boot/dts/renesas/r8a7796-m3ulcb.dts

@@ -169,18 +169,7 @@ &avb {
 	status = "okay";
 
 	phy0: ethernet-phy@0 {
-		rxc-skew-ps = <900>;
-		rxdv-skew-ps = <0>;
-		rxd0-skew-ps = <0>;
-		rxd1-skew-ps = <0>;
-		rxd2-skew-ps = <0>;
-		rxd3-skew-ps = <0>;
-		txc-skew-ps = <900>;
-		txen-skew-ps = <0>;
-		txd0-skew-ps = <0>;
-		txd1-skew-ps = <0>;
-		txd2-skew-ps = <0>;
-		txd3-skew-ps = <0>;
+		rxc-skew-ps = <1500>;
 		reg = <0>;
 		interrupt-parent = <&gpio2>;
 		interrupts = <11 IRQ_TYPE_LEVEL_LOW>;