mm/page_cgroup.c: quiet sparse noise

warning: symbol 'swap_cgroup_ctrl' was not declared. Should it be static?
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Paul Menage <paul@paulmenage.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Balbir Singh <bsingharora@gmail.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_cgroup.c

@@ -360,7 +360,7 @@ struct swap_cgroup_ctrl {
 	spinlock_t	lock;
 };
 
-struct swap_cgroup_ctrl swap_cgroup_ctrl[MAX_SWAPFILES];
+static struct swap_cgroup_ctrl swap_cgroup_ctrl[MAX_SWAPFILES];
 
 struct swap_cgroup {
 	unsigned short		id;