net: add netif_tx_napi_add()

netif_tx_napi_add() is a variant of netif_napi_add()

It should be used by drivers that use a napi structure
to exclusively poll TX.

We do not want to add this kind of napi in napi_hash[] in following
patches, adding generic busy polling to all NAPI drivers.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/wireless/ath/wil6210/netdev.c

@@ -183,7 +183,7 @@ void *wil_if_alloc(struct device *dev)
 
 	netif_napi_add(ndev, &wil->napi_rx, wil6210_netdev_poll_rx,
 		       WIL6210_NAPI_BUDGET);
-	netif_napi_add(ndev, &wil->napi_tx, wil6210_netdev_poll_tx,
+	netif_tx_napi_add(ndev, &wil->napi_tx, wil6210_netdev_poll_tx,
 		       WIL6210_NAPI_BUDGET);
 
 	netif_tx_stop_all_queues(ndev);