[media] v4l2-ctrls/v4l2-controls.h: add MD controls

Add the 'Detect' control class and the new motion detection controls.
Those controls will be used by the solo6x10 and go7007 drivers.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>