powerpc/powernv/ioda: using kfree_rcu() to simplify the code

The callback function of call_rcu() just calls a kfree(), so we
can use kfree_rcu() instead of call_rcu() + callback function.
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190711141818.18044-1-yuehaibing@huawei.com

arch/powerpc/platforms/powernv/pci-ioda-tce.c

@@ -340,14 +340,6 @@ long pnv_pci_ioda2_table_alloc_pages(int nid, __u64 bus_offset,
 	return -ENOMEM;
 }
 
-static void pnv_iommu_table_group_link_free(struct rcu_head *head)
-{
-	struct iommu_table_group_link *tgl = container_of(head,
-			struct iommu_table_group_link, rcu);
-
-	kfree(tgl);
-}
-
 void pnv_pci_unlink_table_and_group(struct iommu_table *tbl,
 		struct iommu_table_group *table_group)
 {
@@ -363,7 +355,7 @@ void pnv_pci_unlink_table_and_group(struct iommu_table *tbl,
 	list_for_each_entry_rcu(tgl, &tbl->it_group_list, next) {
 		if (tgl->table_group == table_group) {
 			list_del_rcu(&tgl->next);
-			call_rcu(&tgl->rcu, pnv_iommu_table_group_link_free);
+			kfree_rcu(tgl, rcu);
 			found = true;
 			break;
 		}