staging: vboxvideo: Move setup of modesetting from driver_load to mode_init

Move the setup of drm modesetting config from vbox_driver_load() to
vbox_mode_init().

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