igb: Add support for byte queue limits.

This adds support for byte queue limits (BQL)

Since this driver collects bytes count in 'bytecount' field, use it also
in igb_tx_map()

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/intel/igb/igb.h b/drivers/net/ethernet/intel/igb/igb.h
index c69feeb..3d12e67 100644
--- a/drivers/net/ethernet/intel/igb/igb.h
+++ b/drivers/net/ethernet/intel/igb/igb.h
@@ -447,4 +447,9 @@
 	return 0;
 }
 
+static inline struct netdev_queue *txring_txq(const struct igb_ring *tx_ring)
+{
+	return netdev_get_tx_queue(tx_ring->netdev, tx_ring->queue_index);
+}
+
 #endif /* _IGB_H_ */