seq_file: constify seq_operations

Make all seq_operations structs const, to help mitigate against
revectoring user-triggerable function pointers.

This is derived from the grsecurity patch, although generated from scratch
because it's simpler than extracting the changes from there.

Signed-off-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/nfs/client.c

@@ -1531,7 +1531,7 @@ static void *nfs_server_list_next(struct seq_file *p, void *v, loff_t *pos);
 static void nfs_server_list_stop(struct seq_file *p, void *v);
 static int nfs_server_list_show(struct seq_file *m, void *v);
 
-static struct seq_operations nfs_server_list_ops = {
+static const struct seq_operations nfs_server_list_ops = {
 	.start	= nfs_server_list_start,
 	.next	= nfs_server_list_next,
 	.stop	= nfs_server_list_stop,
@@ -1552,7 +1552,7 @@ static void *nfs_volume_list_next(struct seq_file *p, void *v, loff_t *pos);
 static void nfs_volume_list_stop(struct seq_file *p, void *v);
 static int nfs_volume_list_show(struct seq_file *m, void *v);
 
-static struct seq_operations nfs_volume_list_ops = {
+static const struct seq_operations nfs_volume_list_ops = {
 	.start	= nfs_volume_list_start,
 	.next	= nfs_volume_list_next,
 	.stop	= nfs_volume_list_stop,