[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/qdio.c b/drivers/s390/cio/qdio.c
index b70039a..7c93a87 100644
--- a/drivers/s390/cio/qdio.c
+++ b/drivers/s390/cio/qdio.c
@@ -2735,7 +2735,7 @@
 	QDIO_DBF_TEXT1(0,trace,dbf_text);
 	QDIO_DBF_TEXT0(0,setup,dbf_text);
 
-	cdev->private->qdio_data = 0;
+	cdev->private->qdio_data = NULL;
 
 	up(&irq_ptr->setting_up_sema);