[S390] cio: allow setting boxed devices offline

Allow users to set boxed devices offline. After setting them
offline, the device state will still be boxed.

Signed-off-by: Peter Oberparleiter <[e-mail]>
Signed-off-by: Martin Schwidefsky <[e-mail]>

drivers/s390/cio/device_fsm.c

···
 		ccw_device_done(cdev, DEV_STATE_NOT_OPER);
 		return 0;
 	}
+	if (cdev->private->state == DEV_STATE_BOXED) {
+		ccw_device_done(cdev, DEV_STATE_BOXED);
+		return 0;
+	}
 	if (ccw_device_is_orphan(cdev)) {
 		ccw_device_done(cdev, DEV_STATE_OFFLINE);
 		return 0;