staging: wfx: fix warning about freeing in-use mutex during device unregister

After hif_shutdown(), communication with the chip is no more possible.
It the only request that never reply. Therefore, hif_cmd.lock is never
unlocked. hif_shutdown() unlock itself hif_cmd.lock to avoid a potential
warning during disposal of device. hif_cmd.key_renew_lock should also
been unlocked for the same reason.
Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200310101356.182818-2-Jerome.Pouiller@silabs.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/wfx/hif_tx.c

@@ -140,6 +140,7 @@ int hif_shutdown(struct wfx_dev *wdev)
 	else
 		control_reg_write(wdev, 0);
 	mutex_unlock(&wdev->hif_cmd.lock);
+	mutex_unlock(&wdev->hif_cmd.key_renew_lock);
 	kfree(hif);
 	return ret;
 }