V4L/DVB (8846): uvcvideo: Supress spurious "EOF in empty payload" trace message

Pass the payload size instead of the header size to uvc_video_decode_end() to
avoid generating an extra trace message for each frame.

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