drm_format_info_plane_cpp() basically just returns the cpp array content
found in the drm_format_info structure.

Since it's pretty trivial, let's remove the function and have the users use
the array directly
Suggested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/c0a78c87cd0410a1819edad2794ad06543c85bb5.1558002671.git-series.maxime.ripard@bootlin.com