sunxi: OrangePi Zero 2: Enable Ethernet

With the fixes to the sun8i-emac driver, we can now enable Ethernet
support on the OrangePi Zero2.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Tested-by: Jernej Skrabec <jernej.skrabec@siol.net>
Reviewed-by: Jernej Skrabec <jernej.skrabec@siol.net>