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>

security/integrity/ima/ima_fs.c

@@ -146,7 +146,7 @@ static int ima_measurements_show(struct seq_file *m, void *v)
 	return 0;
 }
 
-static struct seq_operations ima_measurments_seqops = {
+static const struct seq_operations ima_measurments_seqops = {
 	.start = ima_measurements_start,
 	.next = ima_measurements_next,
 	.stop = ima_measurements_stop,
@@ -221,7 +221,7 @@ static int ima_ascii_measurements_show(struct seq_file *m, void *v)
 	return 0;
 }
 
-static struct seq_operations ima_ascii_measurements_seqops = {
+static const struct seq_operations ima_ascii_measurements_seqops = {
 	.start = ima_measurements_start,
 	.next = ima_measurements_next,
 	.stop = ima_measurements_stop,