xilinx: dts: Remove cdns,zynq-gem

cdns prefix was deprecated and replaced by xlnx one in upstream Linux. Also
U-Boot driver has been updated to support new compatible string that's why
it is time to remove it and deprecate it.

Signed-off-by: Michal Simek <michal.simek@amd.com>
diff --git a/arch/arm/dts/zynq-7000.dtsi b/arch/arm/dts/zynq-7000.dtsi
index 149c644..02cf382 100644
--- a/arch/arm/dts/zynq-7000.dtsi
+++ b/arch/arm/dts/zynq-7000.dtsi
@@ -258,7 +258,7 @@
 		};
 
 		gem0: ethernet@e000b000 {
-			compatible = "xlnx,zynq-gem", "cdns,zynq-gem", "cdns,gem";
+			compatible = "xlnx,zynq-gem", "cdns,gem";
 			reg = <0xe000b000 0x1000>;
 			status = "disabled";
 			interrupts = <0 22 4>;
@@ -269,7 +269,7 @@
 		};
 
 		gem1: ethernet@e000c000 {
-			compatible = "xlnx,zynq-gem", "cdns,zynq-gem", "cdns,gem";
+			compatible = "xlnx,zynq-gem", "cdns,gem";
 			reg = <0xe000c000 0x1000>;
 			status = "disabled";
 			interrupts = <0 45 4>;