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/drivers/char/random.c b/drivers/char/random.c
index af274e5..1756b1f 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -649,7 +649,7 @@
 
 void add_interrupt_randomness(int irq)
 {
-	if (irq >= NR_IRQS || irq_timer_state[irq] == 0)
+	if (irq >= NR_IRQS || irq_timer_state[irq] == NULL)
 		return;
 
 	DEBUG_ENT("irq event %d\n", irq);