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>
diff --git a/drivers/net/ethernet/freescale/gianfar.c b/drivers/net/ethernet/freescale/gianfar.c
index 3e6b9b4..c8bc43e9 100644
--- a/drivers/net/ethernet/freescale/gianfar.c
+++ b/drivers/net/ethernet/freescale/gianfar.c
@@ -1347,12 +1347,12 @@
 		if (priv->poll_mode == GFAR_SQ_POLLING) {
 			netif_napi_add(dev, &priv->gfargrp[i].napi_rx,
 				       gfar_poll_rx_sq, GFAR_DEV_WEIGHT);
-			netif_napi_add(dev, &priv->gfargrp[i].napi_tx,
+			netif_tx_napi_add(dev, &priv->gfargrp[i].napi_tx,
 				       gfar_poll_tx_sq, 2);
 		} else {
 			netif_napi_add(dev, &priv->gfargrp[i].napi_rx,
 				       gfar_poll_rx, GFAR_DEV_WEIGHT);
-			netif_napi_add(dev, &priv->gfargrp[i].napi_tx,
+			netif_tx_napi_add(dev, &priv->gfargrp[i].napi_tx,
 				       gfar_poll_tx, 2);
 		}
 	}