mm, vmscan: fix an outdated comment still mentioning get_scan_ratio

Quite a while ago, get_scan_ratio() has been renamed get_scan_count(),
however a comment in shrink_active_list() still mention it.  This patch
fixes the outdated comment.
Signed-off-by: NJerome Marchand <jmarchan@redhat.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/vmscan.c

@@ -1756,7 +1756,7 @@ static void shrink_active_list(unsigned long nr_to_scan,
 	 * Count referenced pages from currently used mappings as rotated,
 	 * even though only some of them are actually re-activated.  This
 	 * helps balance scan pressure between file and anonymous pages in
-	 * get_scan_ratio.
+	 * get_scan_count.
 	 */
 	reclaim_stat->recent_rotated[file] += nr_rotated;