vfio: ccw: Register mediated device once all structures are initialized

Let's register the mediated device when all the data structures
which could be used are initialized.

Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
Reviewed-by: Eric Farman <farman@linux.ibm.com>
Message-Id: <1540487720-11634-3-git-send-email-pmorel@linux.ibm.com>
Acked-by: Halil Pasic <pasic@linux.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>

drivers/s390/cio/vfio_ccw_drv.c

@@ -134,14 +134,14 @@ static int vfio_ccw_sch_probe(struct subchannel *sch)
 	if (ret)
 		goto out_free;
 
-	ret = vfio_ccw_mdev_reg(sch);
-	if (ret)
-		goto out_disable;
-
 	INIT_WORK(&private->io_work, vfio_ccw_sch_io_todo);
 	atomic_set(&private->avail, 1);
 	private->state = VFIO_CCW_STATE_STANDBY;
 
+	ret = vfio_ccw_mdev_reg(sch);
+	if (ret)
+		goto out_disable;
+
 	return 0;
 
 out_disable: