Fix deinterlacing of packed YUV formats.

Fix deinterlacing of packed YUV formats.

If adding the deinterlacer filter fails, try conversion filters
until we try something the deinterlacer wants, and then try again.
This fixes the problem where the input from the decklink module
(at least with --no-decklink-tenbits) is UYVY, while the deinterlacer only
wants planar formats.

Another possibility would be going straight for the format the
encoder wants, but often, this would be a 4:2:0 format, and 4:2:0
is pretty bad to deinterlace in, since the vertical chroma resolution
is gone already (the chroma interlacing in 4:2:0 is rather odd).