ARM: highbank: enable coherent DMA for xgmac in dts

Enable the xgmac to use the coherent DMA path in highbank.dts
Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

arch/arm/boot/dts/highbank.dts

@@ -308,12 +308,14 @@ ethernet@fff50000 {
 			compatible = "calxeda,hb-xgmac";
 			reg = <0xfff50000 0x1000>;
 			interrupts = <0 77 4  0 78 4  0 79 4>;
+			dma-coherent;
 		};
 
 		ethernet@fff51000 {
 			compatible = "calxeda,hb-xgmac";
 			reg = <0xfff51000 0x1000>;
 			interrupts = <0 80 4  0 81 4  0 82 4>;
+			dma-coherent;
 		};
 
 		combophy0: combo-phy@fff58000 {