media: mc: add manual request completion

media: mc: add manual request completion

By default when the last request object is completed, the whole
request completes as well.

But sometimes you want to delay this completion to an arbitrary point in
time so add a manual complete mode for this.

In req_queue the driver marks the request for manual completion by
calling media_request_mark_manual_completion, and when the driver
wants to manually complete the request it calls
media_request_manual_complete().

Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>
Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>