mm/page_alloc.c:free_area_init_nodes() fix inappropriate use of enum

Local variable `i' is a) misleadingly-named for an `enum zone_type' and b)
used for indexing zones as well as nodes as well as node_maps.

Make it an `int'.
Reported-by: Frans Pop <elendil@planet.nl>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_alloc.c

@@ -3952,7 +3952,7 @@ static void check_for_regular_memory(pg_data_t *pgdat)
 void __init free_area_init_nodes(unsigned long *max_zone_pfn)
 {
 	unsigned long nid;
-	enum zone_type i;
+	int i;
 
 	/* Sort early_node_map as initialisation assumes it is sorted */
 	sort_node_map();