libceph: make ceph_msgr_wq private

The messenger workqueue has no need to be public.  So give it static
scope.

Signed-off-by: Alex Elder <elder@dreamhost.com>
Signed-off-by: Sage Weil <sage@newdream.net>
diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index 04d2b97..31f59ac 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -97,7 +97,7 @@
 /*
  * work queue for all reading and writing to/from the socket.
  */
-struct workqueue_struct *ceph_msgr_wq;
+static struct workqueue_struct *ceph_msgr_wq;
 
 int ceph_msgr_init(void)
 {