staging: vboxvideo: Fold driver_load/unload into probe/remove functions

Fold the driver_load / unload functions into the probe / remove functions
now that we are no longer using the deprecated drm_get_pci_dev() mechanism.

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