Now that we have the vbox drivers sucked into the kernel, advertise this
so that the other vbox drivers can depends on us to provide them and
avoid installing the dkms versions when not needed.

BugLink: http://bugs.launchpad.net/bugs/1434579
BugLink: http://bugs.launchpad.net/bugs/1507588Signed-off-by: Andy Whitcroft <apw@canonical.com>