netdev: Add netdev->addr_list_lock protection.

Add netif_addr_{lock,unlock}{,_bh}() helpers.

Use them to protect operations that operate on or read
the network device unicast and multicast address lists.

Also use them in cases where the code simply wants to
block calls into the driver's ->set_rx_mode() and
->set_multicast_list() methods.

Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/sfc/efx.c

@@ -697,6 +697,8 @@ static void efx_stop_port(struct efx_nic *efx)
 	/* Serialise against efx_set_multicast_list() */
 	if (efx_dev_registered(efx)) {
 		netif_tx_lock_bh(efx->net_dev);
+		netif_addr_lock(efx->net_dev);
+		netif_addr_unlock(efx->net_dev);
 		netif_tx_unlock_bh(efx->net_dev);
 	}
 }