dt-bindings: arm: sunxi: add PineTab Early Adopter edition

Early adopter's PineTabs (and further releases) will have a new LCD
panel different with the one that is used when in development (because
the old panel's supply discontinued).

Add a new DT compatible for it.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20201224024001.19248-1-icenowy@aosc.io