V4L/DVB (6602): V4L: Convert videobuf drivers to videobuf_stop

Drivers were using cookie cutter code for stopping the read/stream.  Use the
new videobuf_stop function which is lock safe.

Signed-off-by: Brandon Philips <bphilips@suse.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>