nfsd: recover: constify nfsd4_client_tracking_ops structures

The nfsd4_client_tracking_ops structures are never modified, so declare
them as const.

Done with the help of Coccinelle.

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Reviewed-by: Jeff Layton <jlayton@poochiereds.net>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h
index d8b16c2..5fbf3bb 100644
--- a/fs/nfsd/netns.h
+++ b/fs/nfsd/netns.h
@@ -92,7 +92,7 @@
 
 	struct file *rec_file;
 	bool in_grace;
-	struct nfsd4_client_tracking_ops *client_tracking_ops;
+	const struct nfsd4_client_tracking_ops *client_tracking_ops;
 
 	time_t nfsd4_lease;
 	time_t nfsd4_grace;