tools/mm/page_owner_sort: fix timestamp comparison for stable sorting

The ternary operator in compare_ts() returns 1 when timestamps are equal,
causing unstable sorting behavior. Replace with explicit three-way
comparison that returns 0 for equal timestamps, ensuring stable qsort
ordering and consistent output.

Link: https://lkml.kernel.org/r/[e-mail]
Fixes: 8f9c447e2e2b ("tools/vm/page_owner_sort.c: support sorting pid and time")
Signed-off-by: Kaushlendra Kumar <[e-mail]>
Cc: Chongxi Zhao <[e-mail]>
Cc: <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

tools/mm/page_owner_sort.c

···
 {
 	const struct block_list *l1 = p1, *l2 = p2;
 
-	return l1->ts_nsec < l2->ts_nsec ? -1 : 1;
+	if (l1->ts_nsec < l2->ts_nsec)
+		return -1;
+	if (l1->ts_nsec > l2->ts_nsec)
+		return 1;
+	return 0;
 }
 
 static int compare_cull_condition(const void *p1, const void *p2)