ipmi_devintf: Add an error return on invalid ioctls

Signed-off-by: Corey Minyard <cminyard@mvista.com>

drivers/char/ipmi/ipmi_devintf.c

@@ -608,6 +608,10 @@ static long ipmi_ioctl(struct file   *file,
 		rv = ipmi_set_maintenance_mode(priv->user, mode);
 		break;
 	}
+
+	default:
+		rv = -ENOTTY;
+		break;
 	}
   
 	return rv;