[S390] Fix sparse warnings.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/kernel/profile.c b/arch/s390/kernel/profile.c
index 7ba777e..b81aa1f 100644
--- a/arch/s390/kernel/profile.c
+++ b/arch/s390/kernel/profile.c
@@ -13,7 +13,7 @@
 void init_irq_proc(void)
 {
 	/* create /proc/irq */
-	root_irq_dir = proc_mkdir("irq", 0);
+	root_irq_dir = proc_mkdir("irq", NULL);
 
 	/* create /proc/irq/prof_cpu_mask */
 	create_prof_cpu_mask(root_irq_dir);