ceph: constify dentry_operations

This makes checkpatch happy.

Signed-off-by: Sage Weil <sage@newdream.net>
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index 95adce4..2482d69 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -861,7 +861,7 @@
 /* dir.c */
 extern const struct file_operations ceph_dir_fops;
 extern const struct inode_operations ceph_dir_iops;
-extern struct dentry_operations ceph_dentry_ops, ceph_snap_dentry_ops,
+extern const struct dentry_operations ceph_dentry_ops, ceph_snap_dentry_ops,
 	ceph_snapdir_dentry_ops;
 
 extern int ceph_handle_notrace_create(struct inode *dir, struct dentry *dentry);