[media] vivid-capture: add control for reduced frame rate

A boolean control Reduced Framerate is added to vivid controls for
controlling the reduced fps option for vivid capture from gui.

Signed-off-by: Prashant Laddha <prladdha@cisco.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>