arm64: allwinner: a64: sopine: add missing ethernet0 alias

The EMAC Ethernet controller was enabled, but an accompanying alias
was not added. This results in unstable numbering if other Ethernet
devices, such as a USB dongle, are present. Also, the bootloader uses
the alias to assign a generated stable MAC address to the device node.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Fixes: 96219b004865 ("arm64: allwinner: a64: add device tree for SoPine
		      with baseboard")
[wens@csie.org: Rewrite commit log as fixing a previous patch with Fixes]
Signed-off-by: Chen-Yu Tsai <wens@csie.org>

arch/arm64/boot/dts/allwinner/sun50i-a64-sopine-baseboard.dts

@@ -53,6 +53,7 @@
 		     "allwinner,sun50i-a64";
 
 	aliases {
+		ethernet0 = &emac;
 		serial0 = &uart0;
 	};