ARM: dts: sun8i: Add ethernet0 alias in Nanopi NEO's device tree

This is required for U-Boot to generate a MAC address for it
automatically.
(Without this, the MAC address will be random on each boot.)

Signed-off-by: Baltazár Radics <baltazar.radics@gmail.com>
Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20220129154214.45629-1-baltazar.radics@gmail.com