[media] v4l: vb2: Avoid double WARN_ON when stopping streaming

The __vb2_queue_cancel function marks the queue as not streaming and
then WARNs when buffers are still owned by the driver. It proceeds to
complete all active buffers by calling vb2_buffer_done with the new
buffer state set to VB2_BUF_STATE_ERROR in that case. This triggers
another WARN_ON due to as new state not being VB2_BUF_STATE_QUEUED while
the queue is not streaming.

Check buffer ownership and complete all active buffers before marking
the queue as not streaming to avoid the double WARN_on.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>