workqueue: deprecate system_nrt[_freezable]_wq

system_nrt[_freezable]_wq are now spurious.  Mark them deprecated and
convert all users to system[_freezable]_wq.

If you're cc'd and wondering what's going on: Now all workqueues are
non-reentrant, so there's no reason to use system_nrt[_freezable]_wq.
Please use system[_freezable]_wq instead.

This patch doesn't make any functional difference.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-By: Lai Jiangshan <laijs@cn.fujitsu.com>

Cc: Jens Axboe <axboe@kernel.dk>
Cc: David Airlie <airlied@linux.ie>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: David Howells <dhowells@redhat.com>
diff --git a/kernel/srcu.c b/kernel/srcu.c
index 2095be3..97c465e 100644
--- a/kernel/srcu.c
+++ b/kernel/srcu.c
@@ -379,7 +379,7 @@
 	rcu_batch_queue(&sp->batch_queue, head);
 	if (!sp->running) {
 		sp->running = true;
-		queue_delayed_work(system_nrt_wq, &sp->work, 0);
+		schedule_delayed_work(&sp->work, 0);
 	}
 	spin_unlock_irqrestore(&sp->queue_lock, flags);
 }
@@ -631,7 +631,7 @@
 	}
 
 	if (pending)
-		queue_delayed_work(system_nrt_wq, &sp->work, SRCU_INTERVAL);
+		schedule_delayed_work(&sp->work, SRCU_INTERVAL);
 }
 
 /*