net: mvpp2: report the tx-usec coalescing information to ethtool

This patch adds the tx-usec value to the informations reported to
ethtool by the get_coalesce function.
Suggested-by: Yan Markman <ymarkman@marvell.com>
Signed-off-by: Antoine Tenart <antoine.tenart@free-electrons.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/marvell/mvpp2.c

@@ -7327,6 +7327,7 @@ static int mvpp2_ethtool_get_coalesce(struct net_device *dev,
 	c->rx_coalesce_usecs       = port->rxqs[0]->time_coal;
 	c->rx_max_coalesced_frames = port->rxqs[0]->pkts_coal;
 	c->tx_max_coalesced_frames = port->txqs[0]->done_pkts_coal;
+	c->tx_coalesce_usecs       = port->tx_time_coal;
 	return 0;
 }