[media] davinci: vpif: missing unlocks on error

We recently changed some locking around so we need some new unlocks on
the error paths.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>