[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/drivers/s390/cio/ccwgroup.c b/drivers/s390/cio/ccwgroup.c
index c7319a0..f26a2ee 100644
--- a/drivers/s390/cio/ccwgroup.c
+++ b/drivers/s390/cio/ccwgroup.c
@@ -319,7 +319,7 @@
 	if (!try_module_get(gdrv->owner))
 		return -EINVAL;
 
-	value = simple_strtoul(buf, 0, 0);
+	value = simple_strtoul(buf, NULL, 0);
 	ret = count;
 	if (value == 1)
 		ccwgroup_set_online(gdev);