ARM: dts: rockchip: Setup rk3066/rk3188 ethernet0 alias for u-boot

Add an ethernet0 alias for the RK3066/RK3188 mac interface so
that u-boot can find the device-node and fill in the mac address on
boards that support a wired network interface.
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm/boot/dts/rk3xxx.dtsi

@@ -49,6 +49,7 @@ / {
 	interrupt-parent = <&gic>;
 
 	aliases {
+		ethernet0 = &emac;
 		i2c0 = &i2c0;
 		i2c1 = &i2c1;
 		i2c2 = &i2c2;