arm64: zynqmp: Define phy-mode in zcu1275-revB

Add missing required phy-mode property.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/fdd98ebd217e005fedde6aa2175449f7ad5555eb.1726219714.git.michal.simek@amd.com
diff --git a/arch/arm/dts/zynqmp-zcu1275-revB.dts b/arch/arm/dts/zynqmp-zcu1275-revB.dts
index 4060dc3..ed83ba3 100644
--- a/arch/arm/dts/zynqmp-zcu1275-revB.dts
+++ b/arch/arm/dts/zynqmp-zcu1275-revB.dts
@@ -43,6 +43,7 @@
 
 &gem1 {
 	status = "okay";
+	phy-mode = "rgmii-id";
 	mdio {
 		#address-cells = <1>;
 		#size-cells = <0>;