media: v4l2-ctrls: Fix doc for v4l2_ctrl_request_hdl_find

We should call v4l2_ctrl_request_hdl_put() instead of
v4l2_ctrl_request_put_hdl(). Fix the typo.

Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Reviewed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>