sfc: Remove bogus call to efx_release_tx_buffers()

efx_unregister_netdev() should not call efx_release_tx_buffers()
directly, as it is already done when closing the device:
efx_net_stop() -> efx_stop_all() -> efx_stop_datapath() ->
efx_fini_tx_queue() -> efx_release_tx_buffers().

(This was presumably a workaround for a race between efx_stop_all()
and the data path that has since been properly fixed.)
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

drivers/net/ethernet/sfc/efx.c

@@ -2156,22 +2156,11 @@ static int efx_register_netdev(struct efx_nic *efx)
 
 static void efx_unregister_netdev(struct efx_nic *efx)
 {
-	struct efx_channel *channel;
-	struct efx_tx_queue *tx_queue;
-
 	if (!efx->net_dev)
 		return;
 
 	BUG_ON(netdev_priv(efx->net_dev) != efx);
 
-	/* Free up any skbs still remaining. This has to happen before
-	 * we try to unregister the netdev as running their destructors
-	 * may be needed to get the device ref. count to 0. */
-	efx_for_each_channel(channel, efx) {
-		efx_for_each_channel_tx_queue(tx_queue, channel)
-			efx_release_tx_buffers(tx_queue);
-	}
-
 	strlcpy(efx->name, pci_name(efx->pci_dev), sizeof(efx->name));
 	device_remove_file(&efx->pci_dev->dev, &dev_attr_phy_type);