[media] v4l2-ctrls: Add v4l2_ctrl_[gs]_ctrl_int64()

These helper functions get and set a 64-bit control's value from within
a driver. They are similar to v4l2_ctrl_[gs]_ctrl() but operate on
64-bit integer controls instead of 32-bit controls.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>