Fix strange uses of MAX_NR_ZONES

Sometimes we use MAX_NR_ZONES - x to refer to a zone. Make that
explicit.

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

Index: linux-2.6.17-mm6/arch/x86_64/mm/init.c
===================================================================
--- linux-2.6.17-mm6.orig/arch/x86_64/mm/init.c	2006-07-03 13:47:14.329487884 -0700
+++ linux-2.6.17-mm6/arch/x86_64/mm/init.c	2006-07-03 14:33:13.479261596 -0700
@@ -536,7 +536,7 @@ int memory_add_physaddr_to_nid(u64 start
 int arch_add_memory(int nid, u64 start, u64 size)
 {
 	struct pglist_data *pgdat = NODE_DATA(nid);
-	struct zone *zone = pgdat->node_zones + MAX_NR_ZONES-2;
+	struct zone *zone = pgdat->node_zones + ZONE_NORMAL;
 	unsigned long start_pfn = start >> PAGE_SHIFT;
 	unsigned long nr_pages = size >> PAGE_SHIFT;
 	int ret;
Index: linux-2.6.17-mm6/arch/i386/mm/init.c
===================================================================
--- linux-2.6.17-mm6.orig/arch/i386/mm/init.c	2006-07-03 13:47:12.740718955 -0700
+++ linux-2.6.17-mm6/arch/i386/mm/init.c	2006-07-03 14:33:13.481214600 -0700
@@ -657,7 +657,7 @@ void __init mem_init(void)
 int arch_add_memory(int nid, u64 start, u64 size)
 {
 	struct pglist_data *pgdata = &contig_page_data;
-	struct zone *zone = pgdata->node_zones + MAX_NR_ZONES-1;
+	struct zone *zone = pgdata->node_zones + ZONE_HIGHMEM;
 	unsigned long start_pfn = start >> PAGE_SHIFT;
 	unsigned long nr_pages = size >> PAGE_SHIFT;