V4L/DVB: STV0288 Incorrect bit sample for Vitterbi status

bit 3(LK) indicates that the Vstatus is locked.
Currently using bit 7(CF) which is usually present, results in early
aborted search in FEC_AUTO and missing channels.

Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Cc: Igor M. Liplianin <liplianin@me.by>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>