staging: vboxvideo: Remove vboxfb_create_object() wrapper

The vboxfb_create_object() wrapper really does nothing more then just
call vbox_gem_create(), so this commit drops it, replacing it with
a direct call to vbox_gem_create().

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