libcamera: v4l2_videodevice: Signal buffer completion at streamoff time

When stopping the stream buffers have been queued, in which case their
completion is never be notified to the user. This can lead to memory
leaks. Fix it by notifying completion of all queued buffers with the
status set to error.

As a result the base PipelineHandler implementation can be simplified,
as all requests complete as the result of stopping the stream. The
stop() method that manually completes all queued requests isn't needed
anymore.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

src/libcamera/include/pipeline_handler.h

@@ -74,7 +74,7 @@ public:
 				const std::set<Stream *> &streams) = 0;
 
 	virtual int start(Camera *camera) = 0;
-	virtual void stop(Camera *camera);
+	virtual void stop(Camera *camera) = 0;
 
 	virtual int queueRequest(Camera *camera, Request *request);