proc: use macro in /proc/latency hook

->latency_record is defined as

	struct latency_record[LT_SAVECOUNT];

so use the same macro whie iterating.

Link: http://lkml.kernel.org/r/20180627200534.GA18434@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/proc/base.c

@@ -463,7 +463,7 @@ static int lstats_show_proc(struct seq_file *m, void *v)
 	if (!task)
 		return -ESRCH;
 	seq_puts(m, "Latency Top version : v0.1\n");
-	for (i = 0; i < 32; i++) {
+	for (i = 0; i < LT_SAVECOUNT; i++) {
 		struct latency_record *lr = &task->latency_record[i];
 		if (lr->backtrace[0]) {
 			int q;