V4L/DVB (10101): uvcvideo: Fix bulk URB processing when the header is erroneous

When the first bulk URB of a video payload contains an erroneous header, or
when no V4L2 buffer is available, the whole payload must be dropped. Change
the skip logic to drop all bulk URBs until the end of the payload instead of
the first one only.

Signed-off-by: Laurent Pinchart <laurent.pinchart@skynet.be>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>