CD 155f0680-aa44-49a8-a2ec-e1a341fc55fe

These 2 extra conversions (CVPX_X to CVPX_RGBA and CVPX_RGBA to CVPX_X) will be
done only if ci_filters doesn't accept the input chroma. This won't happen
often since videotoolbox will most likely output chromas that can be accepted
by ci_filters.

This was not never touched since the initial commit and was not up to date.

(cherry picked from commit 4e803da8

)
Signed-off-by: Thomas Guillem <thomas@gllm.fr>