[media] s5p-fimc: Fix locking in subdev set_crop op

When setting TRY crop on the sub-device the mutex was erroneously acquired
rather than released on exit path. This bug is present in kernels starting
from v3.2.

Cc: stable@vger.kernel.org
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>