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>
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 213b7f9..cd83d99 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2314,7 +2314,7 @@
 	return seq_printf(s, "%d\n", *(int *)v);
 }
 
-static struct seq_operations cgroup_tasks_seq_operations = {
+static const struct seq_operations cgroup_tasks_seq_operations = {
 	.start = cgroup_tasks_start,
 	.stop = cgroup_tasks_stop,
 	.next = cgroup_tasks_next,