ceph: clean up header guards

Signed-off-by: Sage Weil <sage@newdream.net>
diff --git a/fs/ceph/msgr.h b/fs/ceph/msgr.h
index 892a029..680d3d6 100644
--- a/fs/ceph/msgr.h
+++ b/fs/ceph/msgr.h
@@ -1,5 +1,5 @@
-#ifndef __MSGR_H
-#define __MSGR_H
+#ifndef CEPH_MSGR_H
+#define CEPH_MSGR_H
 
 /*
  * Data types for message passing layer used by Ceph.