media: exynos4-is: Fix recursive locking in isp_video_release()

>From isp_video_release(), &isp->video_lock is held and subsequent
vb2_fop_release() tries to lock vdev->lock which is same with the
previous one. Replace vb2_fop_release() with _vb2_fop_release() to
fix the recursive locking.

Fixes: 1380f575

 ("[media] videobuf2: Add missing lock held on vb2_fop_release")
Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
Reviewed-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>