[rbp/omxplayer] Support automatic deinterlace correctly

Previously there was no distinction between deinterlace being automatic and forced on.
Both did a hacky parse that only worked (sometimes) for h264. Other codecs (e.g. MPEG2) would always be forced on.

This change now handles the three modes correctly. Off and force on do as expected.
Automatic now queries the openmax video codec, which can reliably determine if a stream is interlaced.