[media] saa7164: fix poll bugs
[media] saa7164: fix poll bugs

- poll doesn't return negative values, so you can't return -EINVAL.
  Instead return POLLERR.
- poll can't be called if !video_is_registered(), so this test can
  be dropped.
- poll can never do a blocking wait, so remove that check.
- poll shouldn't attempt to start streaming if the caller isn't interested
  in read events.

Signed-off-by: Hans Verkuil <3a513708f73c27e7d36ebc496aa41dad6a3153ea@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <ad86ba2154032c9f55743a190faa2459a9d61d42@osg.samsung.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs