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/fs/autofs/waitq.c b/fs/autofs/waitq.c
index 19a9caf..be46805 100644
--- a/fs/autofs/waitq.c
+++ b/fs/autofs/waitq.c
@@ -182,7 +182,7 @@
 {
 	struct autofs_wait_queue *wq, **wql;
 
-	for ( wql = &sbi->queues ; (wq = *wql) != 0 ; wql = &wq->next ) {
+	for (wql = &sbi->queues; (wq = *wql) != NULL; wql = &wq->next) {
 		if ( wq->wait_queue_token == wait_queue_token )
 			break;
 	}