drm/sun4i: frontend: Add support for packed YUV422 input formats

This introduces support for packed YUV formats with 4:2:2 sampling using
the frontend. Definitions are introduced for the data format and pixel
sequence input format register values.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190118145133.21281-9-paul.kocialkowski@bootlin.com