[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/char/raw3270.h b/drivers/s390/char/raw3270.h
index b635bf8..90beaa8 100644
--- a/drivers/s390/char/raw3270.h
+++ b/drivers/s390/char/raw3270.h
@@ -231,7 +231,7 @@
 		INIT_LIST_HEAD(&cs->update);
 		return cs;
 	}
-	return 0;
+	return NULL;
 }
 
 static inline unsigned long