zone_statitics: Use hot node instead of cold zone_pgdat

Now that we have the node in the hot zone of struct zone we can avoid accessing
zone_pgdat in zone_statistics.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.18-rc6-mm2/mm/vmstat.c
===================================================================
--- linux-2.6.18-rc6-mm2.orig/mm/vmstat.c	2006-09-18 21:24:50.000000000 -0500
+++ linux-2.6.18-rc6-mm2/mm/vmstat.c	2006-09-18 21:25:48.793059949 -0500
@@ -370,7 +370,7 @@ void zone_statistics(struct zonelist *zo
 		__inc_zone_state(z, NUMA_MISS);
 		__inc_zone_state(zonelist->zones[0], NUMA_FOREIGN);
 	}
-	if (z->zone_pgdat == NODE_DATA(numa_node_id()))
+	if (z->node == numa_node_id())
 		__inc_zone_state(z, NUMA_LOCAL);
 	else
 		__inc_zone_state(z, NUMA_OTHER);