ARM: dts: rk312x: Add ethernet alias for uboot write MAC address

Now we use U-Boot to write the MAC address into DTB, to
solve the problem of getting the MAC address in the vendor
partition too late at the kernel level, so the Ethernet
alias is added for U-Boot to quickly find the gmac DTB node.

Signed-off-by: David Wu <david.wu@rock-chips.com>
Change-Id: Ibeae8b4cc09bbf3cfb7b64e51f6f6aa35820bf0d

arch/arm/boot/dts/rk312x.dtsi

@@ -56,6 +56,7 @@
 	#size-cells = <1>;
 
 	aliases {
+		ethernet0 = &gmac;
 		serial0 = &uart0;
 		serial1 = &uart1;
 		serial2 = &uart2;