drivers: video: fix a typo in get_ctrl API function type

The "struct video_driver_api" struct field "get_ctrl" had the wrong type
although this did not have any practical effect as "video_api_set_ctrl_t"
and "video_api_get_ctrl_t" have the same signature.

Signed-off-by: Josuah Demangeon <me@josuah.net>