[media] usbtv: Fix deinterlacing

The image data is laid out a bit more weirdly and thus needs more work to
properly interlace. What we get from hardware is V4L2_FIELD_ALTERNATE, but
since userspace support for it is practically nonexistent, thus we make
V4L2_FIELD_INTERLACED from it so that it's more easily interpreted.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Cc: Hans Verkuil <hans.verkuil@cisco.com>
Cc: Mauro Carvalho Chehab <mchehab@redhat.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-media@vger.kernel.org
[media] usbtv: Throw corrupted frames away

Ignore out of order data and mark incomplete buffers as errored.
This gets rid of annoying flicker due to occassional garbage from hardware.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Cc: Hans Verkuil <hans.verkuil@cisco.com>
Cc: Mauro Carvalho Chehab <mchehab@redhat.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-media@vger.kernel.org