nfsd: constify nfsd4_callback_ops structure

The nfsd4_callback_ops structure is never modified, so declare it as const.

Done with the help of Coccinelle.

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 6b800b5b..0d30a36 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -98,7 +98,7 @@
 
 static void free_session(struct nfsd4_session *);
 
-static struct nfsd4_callback_ops nfsd4_cb_recall_ops;
+static const struct nfsd4_callback_ops nfsd4_cb_recall_ops;
 
 static bool is_session_dead(struct nfsd4_session *ses)
 {
@@ -3648,7 +3648,7 @@
 	nfs4_put_stid(&dp->dl_stid);
 }
 
-static struct nfsd4_callback_ops nfsd4_cb_recall_ops = {
+static const struct nfsd4_callback_ops nfsd4_cb_recall_ops = {
 	.prepare	= nfsd4_cb_recall_prepare,
 	.done		= nfsd4_cb_recall_done,
 	.release	= nfsd4_cb_recall_release,