workqueue: remove deprecated WQ_NON_REENTRANT

Tejun Heo has made WQ_NON_REENTRANT useless in the dbf2576e37
("workqueue: make all workqueues non-reentrant"). So remove its
usages and definition.

This patch doesn't introduce any behavior changes.

tj: minor description updates.

Signed-off-by: ZhangZhen <zhenzhang.zhang@huawei.com>
Sigend-off-by: Tejun Heo <tj@kernel.org>
Acked-by: James Chapman <jchapman@katalix.com>
Acked-by: Ulf Hansson <ulf.hansson@linaro.org>
diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index 735d0f6..fcbd63e 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -2016,7 +2016,7 @@
 	if (rc)
 		goto out;
 
-	l2tp_wq = alloc_workqueue("l2tp", WQ_NON_REENTRANT | WQ_UNBOUND, 0);
+	l2tp_wq = alloc_workqueue("l2tp", WQ_UNBOUND, 0);
 	if (!l2tp_wq) {
 		pr_err("alloc_workqueue failed\n");
 		rc = -ENOMEM;