vhost-vdpa: fix vhost_vdpa_map() on error condition

vhost_vdpa_map() should remove the iotlb entry just added
if the corresponding mapping fails to set up properly.

Fixes: 4c8cf31 ("vhost: introduce vDPA-based backend")
Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
Link: https://lore.kernel.org/r/1601701330-16837-2-git-send-email-si-wei.liu@oracle.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vhost/vdpa.c

@@ -565,6 +565,9 @@ static int vhost_vdpa_map(struct vhost_vdpa *v,
 			      perm_to_iommu_flags(perm));
 	}
 
+	if (r)
+		vhost_iotlb_del_range(dev->iotlb, iova, iova + size - 1);
+
 	return r;
 }