[COMMON] media: smfc: cancel queued buffers in .stop_streaming()

[COMMON] media: smfc: cancel queued buffers in .stop_streaming()

stop_streaming() waits for all queued buffers to be finished. But SMFC
driver as a mem2mem device, may wait for the queued buffer of the
current vb2_queue while no buffer is queued in the other vb2_queue.
If .stop_streaming() is called in that situation, it waits for a
buffer to be queued to the other vb2_queue infinitely.
However it will never happen because no user will queue a buffer
during stopping operations on the device. Therefore, the driver
should see if other vb2_queue has a queued buffer when this vb2_queue
is stopping streaming. If the other vb2_queue has no queued buffer,
stop_streaming() should cancel all queued buffers in the current
vb2_queue.

Change-Id: I3b07916707a0b0d238a3238621fea631df8b942d
Signed-off-by: Cho KyongHo <pullip.cho@samsung.com>