[media] s5p-fimc: Update to the control handler lock changes

Commit 77e7c4e6
"v4l: Allow changing control handler lock" changed
the lock field of struct v4l2_ctrl_handler to a pointer
and this driver wasn't updated properly. This patch fixes
following warning:

drivers/media/video/s5p-fimc/fimc-core.c: In function ‘fimc_ctrls_activate’:
drivers/media/video/s5p-fimc/fimc-core.c:644: warning: passing argument 1 of ‘mutex_lock’ from incompatible pointer type
include/linux/mutex.h:152: note: expected ‘struct mutex *’ but argument is of type ‘struct mutex **’
drivers/media/video/s5p-fimc/fimc-core.c:663: warning: passing argument 1 of ‘mutex_unlock’ from incompatible pointer type
include/linux/mutex.h:169: note: expected ‘struct mutex *’ but argument is of type ‘struct mutex **’

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>