Bluetooth: hci_nokia: prevent crash on module removal

Only cancel any ongoing work after making sure, that no new work
can be scheduled. This fixes a race condition in the remove handler.
Signed-off-by: Ian Molton <ian@mnementh.co.uk>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

drivers/bluetooth/hci_nokia.c

@@ -770,10 +770,12 @@ static void nokia_bluetooth_serdev_remove(struct serdev_device *serdev)
 	struct hci_uart *hu = &btdev->hu;
 	struct hci_dev *hdev = hu->hdev;
 
-	cancel_work_sync(&hu->write_work);
 
 	hci_unregister_dev(hdev);
 	hci_free_dev(hdev);
+
+	cancel_work_sync(&hu->write_work);
+
 	hu->proto->close(hu);
 
 	pm_runtime_disable(&btdev->serdev->dev);