arm64: dts: rockchip: Setup rk3368 ethernet0 alias for u-boot

Add an ethernet0 alias for the RK3368 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/arm64/boot/dts/rockchip/rk3368.dtsi

@@ -53,6 +53,7 @@ / {
 	#size-cells = <2>;
 
 	aliases {
+		ethernet0 = &gmac;
 		i2c0 = &i2c0;
 		i2c1 = &i2c1;
 		i2c2 = &i2c2;