sparse pointer use of zero as null

Get rid of sparse related warnings from places that use integer as NULL
pointer.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Cc: Andi Kleen <ak@suse.de>
Cc: Jeff Garzik <jeff@garzik.org>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Ian Kent <raven@themaw.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Davide Libenzi <davidel@xmailserver.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/vmscan.c b/mm/vmscan.c
index e147138..cb474cc 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1282,7 +1282,7 @@
 	 */
 	if (priority < 0)
 		priority = 0;
-	for (i = 0; zones[i] != 0; i++) {
+	for (i = 0; zones[i] != NULL; i++) {
 		struct zone *zone = zones[i];
 
 		if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))