drm/sun4i: Add a few formats

The planes can do more than what was previously exposed. Add support for
them.

Since we still have the issue that the primary plane cannot have any alpha
component, we will expose only the non-alpha formats in the primary
formats, and the alpha formats will be exposed in the overlays.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Chen-Yu Tsai <wens@csie.org>