vfio/type1: Add conditional rescheduling after iommu map failed

Commit c5e66887 ("vfio/type1: Add conditional rescheduling")
missed a "cond_resched()" in vfio_iommu_map if iommu map failed.

This is a very tiny optimization and the case can hardly happen.
Signed-off-by: Xiang Zheng <zhengxiang9@huawei.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/vfio/vfio_iommu_type1.c

@@ -1225,8 +1225,10 @@ static int vfio_iommu_map(struct vfio_iommu *iommu, dma_addr_t iova,
 	return 0;
 
 unwind:
-	list_for_each_entry_continue_reverse(d, &iommu->domain_list, next)
+	list_for_each_entry_continue_reverse(d, &iommu->domain_list, next) {
 		iommu_unmap(d->domain, iova, npage << PAGE_SHIFT);
+		cond_resched();
+	}
 
 	return ret;
 }