ARM: at91/dt: sama5d3 xplained: add phy address for macb0

Specify the phy address on macb0 node aka GEM.
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>

arch/arm/boot/dts/at91-sama5d3_xplained.dts

@@ -105,7 +105,13 @@ vddana_reg: LDO_REG2 {
 
 			macb0: ethernet@f0028000 {
 				phy-mode = "rgmii";
+				#address-cells = <1>;
+				#size-cells = <0>;
 				status = "okay";
+
+				ethernet-phy@7 {
+					reg = <0x7>;
+				};
 			};
 
 			pwm0: pwm@f002c000 {