V4L/DVB: videodev2.h: move definition of enum v4l2_ctrl_type to the other control types

For some reason the definition of enum v4l2_ctrl_type is far from the
place where it is actually needed. This makes it hard to work with this
header.

Move it to just before struct v4l2_queryctrl, which is the one that
actually uses it.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>