mm: make scan_zone_unevictable_pages() static

sparse output following warning

	mm/vmscan.c:2507:6: warning: symbol 'scan_zone_unevictable_pages' was not declared. Should it be static?

cleanup here.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 062767d..1ef5a2e 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2464,7 +2464,7 @@
  * back onto @zone's unevictable list.
  */
 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
-void scan_zone_unevictable_pages(struct zone *zone)
+static void scan_zone_unevictable_pages(struct zone *zone)
 {
 	struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
 	unsigned long scan;