HID: elo: kill not flush the work

Flushing a work that reschedules itself is not a sensible operation. It needs
to be killed. Failure to do so leads to a kernel panic in the timer code.

CC: [e-mail]
Signed-off-by: Oliver Neukum <[e-mail]>
Reviewed-by: Benjamin Tissoires <[e-mail]>
Signed-off-by: Jiri Kosina <[e-mail]>

drivers/hid/hid-elo.c

···
 	struct elo_priv *priv = hid_get_drvdata(hdev);
 
 	hid_hw_stop(hdev);
-	flush_workqueue(wq);
+	cancel_delayed_work_sync(&priv->work);
 	kfree(priv);
 }