[media] v4l: ctrls: Move control lock/unlock above the control access functions

The v4l2_ctrl_{,un}lock will be needed elsewhere. Define them before the
functions that perform operations on controls.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>