mm: make setup_per_zone_inactive_ratio() static

Sparse output following warning.

mm/page_alloc.c:4301:6: warning: symbol 'setup_per_zone_inactive_ratio' was not declared. Should it be static?

cleanup here.
Signed-off-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/page_alloc.c

@@ -4314,7 +4314,7 @@ void setup_per_zone_pages_min(void)
  *    1TB     101        10GB
  *   10TB     320        32GB
  */
-void setup_per_zone_inactive_ratio(void)
+static void setup_per_zone_inactive_ratio(void)
 {
 	struct zone *zone;