[media] media/v4l2-core: struct struct v4l2_ext_controls param which

Support for new field which on v4l2_ext_controls, used to get the
default value of one or more controls.

Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>