[media] videodev2.h: add struct v4l2_query_ext_ctrl and VIDIOC_QUERY_EXT_CTRL

Add a new struct and ioctl to extend the amount of information you can
get for a control.

The range is now a s64 type, and array dimensions and element size can be
reported through nr_of_dims/dims/elems/elem_size.

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