arm64: allwinner: a64: pine64: add missing ethernet0 alias

arm64: allwinner: a64: pine64: 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: 970239437493 ("arm64: allwinner: pine64: Enable dwmac-sun8i")
[wens@csie.org: Rewrite commit log as fixing a previous patch with Fixes]
Signed-off-by: Chen-Yu Tsai <wens@csie.org>