staging: vboxvideo: Cleanup the comments

Some comments where still using docbook style comments, move these
either over to kerneldoc, or just make them regular comments.

Also remove a bunch of obsolete comments.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>