Commit 6c8268db broke recording
from interlaced v4l2 source (e.g. typical tv capture card) since
V4L2_FIELD_SEQ_TB (with fields stored separately) does not map
to currently defined interlaced format (fields stored interleaved).

Besides this mismatch, hardware might quite likely not support or
appreciate this field value, since querying supported formats mapped
_INTERLACED field formats to interlaced=true caps (so the latter should
not be mapped to field value that is not known to be supported).