[media] s5p-fimc: fimc-lite: Prevent deadlock at STREAMON/OFF ioctls

[media] s5p-fimc: fimc-lite: Prevent deadlock at STREAMON/OFF ioctls

This patch fixes regression introduced in commit 6319d6a002beb26631
'[media] fimc-lite: Add ISP FIFO output support'.
In case of a configuration where video is captured at the video node
exposed by the FIMC-LITE driver there is a following video pipeline:
sensor -> MIPI-CSIS.n -> FIMC-LITE.n subdev -> FIMC-LITE.n video node
In this situation s_stream() handler of the FIMC-LITE.n is called
back from within VIDIOC_STREAMON/OFF ioctl of the FIMC-LITE.n video
node, through vb2_stream_on/off(), start/stop_streaming and
fimc_pipeline_call(set_stream). The fimc->lock mutex is already held
then, before invoking vidioc_streamon/off. So it must not be taken
again in the s_stream() callback in this case, to avoid a deadlock.
This patch makes fimc->out_path atomic_t so the mutex don't need
to be taken in the FIMC-LITE subdev s_stream() callback in the DMA
output case.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyugmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>