avcodec_enum_to_chroma_pos() and avcodec_chroma_pos_to_enum()
deal with enum AVChromaLocation which is defined in lavu.
These functions are therefore replaced by
av_chroma_location_enum_to_pos() and av_chroma_location_pos_to_enum().
This commit provides the necessary deprecations. Also already make
these functions wrappers around the corresponding lavu functions
as not doing so would force one to disable deprecation warnings.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>