[media] tm6000: fix G/TRY_FMT

Two fixes:
- the priv field wasn't set to 0.
- only V4L2_FIELD_INTERLACED is supported.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>