workqueue: avoid using deprecated functions

The network merge brought in a few users of functions that got
deprecated by the workqueue cleanups: the 'system_nrt_wq' is now the
same as the regular system_wq, since all workqueues are now non-
reentrant.

Similarly, remove one use of flush_work_sync() - the regular
flush_work() has become synchronous, and the "_sync()" version is thus
deprecated as being superfluous.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/net/nfc/core.c b/net/nfc/core.c
index c9eacc1..479bee3 100644
--- a/net/nfc/core.c
+++ b/net/nfc/core.c
@@ -715,7 +715,7 @@
 {
 	struct nfc_dev *dev = (struct nfc_dev *)data;
 
-	queue_work(system_nrt_wq, &dev->check_pres_work);
+	schedule_work(&dev->check_pres_work);
 }
 
 struct class nfc_class = {