s390/dasd: fix ioctl return value

For unimplemented ioctls the dasd driver should return -ENOTTY.

Reported-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>
Acked-by: Stefan Weinhuber <wein@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/drivers/s390/block/dasd_ioctl.c b/drivers/s390/block/dasd_ioctl.c
index cceae70..654c692 100644
--- a/drivers/s390/block/dasd_ioctl.c
+++ b/drivers/s390/block/dasd_ioctl.c
@@ -498,12 +498,9 @@
 		break;
 	default:
 		/* if the discipline has an ioctl method try it. */
-		if (base->discipline->ioctl) {
+		rc = -ENOTTY;
+		if (base->discipline->ioctl)
 			rc = base->discipline->ioctl(block, cmd, argp);
-			if (rc == -ENOIOCTLCMD)
-				rc = -EINVAL;
-		} else
-			rc = -EINVAL;
 	}
 	dasd_put_device(base);
 	return rc;