cgroup: remove use of seq_printf return value

The seq_printf return value, because it's frequently misused,
will eventually be converted to void.

See: commit 1f33c41c ("seq_file: Rename seq_overflow() to
     seq_has_overflowed() and make public")
Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/cgroup.c

@@ -4196,7 +4196,9 @@ static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
 
 static int cgroup_pidlist_show(struct seq_file *s, void *v)
 {
-	return seq_printf(s, "%d\n", *(int *)v);
+	seq_printf(s, "%d\n", *(int *)v);
+
+	return 0;
 }
 
 static u64 cgroup_read_notify_on_release(struct cgroup_subsys_state *css,