Use the pgdat pointer we've already defined in wakeup_kswapd

Signed-off-by: Con Kolivas <kernel@kolivas.org>

Index: linux-2.6.13-mm2/mm/vmscan.c
===================================================================
--- linux-2.6.13-mm2.orig/mm/vmscan.c	2005-09-09 01:27:33.000000000 +1000
+++ linux-2.6.13-mm2/mm/vmscan.c	2005-09-09 01:28:56.000000000 +1000
@@ -1263,9 +1263,9 @@ void wakeup_kswapd(struct zone *zone, in
 		pgdat->kswapd_max_order = order;
 	if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
 		return;
-	if (!waitqueue_active(&zone->zone_pgdat->kswapd_wait))
+	if (!waitqueue_active(&pgdat->kswapd_wait))
 		return;
-	wake_up_interruptible(&zone->zone_pgdat->kswapd_wait);
+	wake_up_interruptible(&pgdat->kswapd_wait);
 }
 
 #ifdef CONFIG_PM