V4L/DVB: usbvision: remove non-working vbi device

The usbvision driver created vbi device nodes but the actual implementation
was just stubs and only returned errors to userspace.

In addition it used video_usercopy() and we want to remove that eventually.

So remove all the vbi code except for the vbi flag in the card definition
should someone ever be mad enough to work on a proper implementation for this
driver.

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