media: videobuf2-core: add uses_requests/qbuf flags

Set the first time a buffer from a request is queued to vb2
(uses_requests) or directly queued (uses_qbuf).
Cleared when the queue is canceled.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>