ceph: WQ_NON_REENTRANT is meaningless and going away

dbf2576e ("workqueue: make all workqueues non-reentrant") made
WQ_NON_REENTRANT no-op and the flag is going away.  Remove its usages.

This patch doesn't introduce any behavior changes.
Signed-off-by: NTejun Heo <tj@kernel.org>
Reviewed-by: NSage Weil <sage@inktank.com>
Cc: ceph-devel@vger.kernel.org

net/ceph/messenger.c

@@ -290,7 +290,7 @@ int ceph_msgr_init(void)
 	if (ceph_msgr_slab_init())
 		return -ENOMEM;
 
-	ceph_msgr_wq = alloc_workqueue("ceph-msgr", WQ_NON_REENTRANT, 0);
+	ceph_msgr_wq = alloc_workqueue("ceph-msgr", 0, 0);
 	if (ceph_msgr_wq)
 		return 0;