drm/sun4i: Wire in DE2 YUV support

Now that we have all required bits, add support for YUV formats.

DRM subsystem doesn't know YUV411 semi-planar format, so leave that out
for now.

Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171201060550.10392-27-jernej.skrabec@siol.net