vdpa/mlx5: Restore cur_num_vqs in case of failure in change_num_qps()

Restore ndev->cur_num_vqs to the original value in case change_num_qps()
fails.

Fixes: 5289373 ("vdpa/mlx5: Add multiqueue support")
Reviewed-by: Si-Wei Liu<si-wei.liu@oracle.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Eli Cohen <elic@nvidia.com>
Link: https://lore.kernel.org/r/20220105114646.577224-10-elic@nvidia.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Author: elic307i

drivers/vdpa/mlx5/net/mlx5_vnet.c

@@ -1541,9 +1541,11 @@ static int change_num_qps(struct mlx5_vdpa_dev *mvdev, int newqps)
 	return 0;
 
 clean_added:
-	for (--i; i >= cur_qps; --i)
+	for (--i; i >= 2 * cur_qps; --i)
 		teardown_vq(ndev, &ndev->vqs[i]);
 
+	ndev->cur_num_vqs = 2 * cur_qps;
+
 	return err;
 }