reviewed again. I still don't like this as it introduces an unbalanced weighting for the
vfio dd but ... We could consider removing the
if (ap_drv->flags & AP_DRIVER_FLAG_DEFAULT)
return 0;
in function __verify_queue_reservations. It would still work as the 'default device
drivers' do not implement the in_use() callback and thus do not disagree about
the upcoming change.