ehea: Update multiqueue support

The ehea driver had some multiqueue support but was missing the last
few years of networking stack improvements:

- Use skb_record_rx_queue to record which queue an skb came in on.

- Remove the driver specific netif_queue lock and use the networking
  stack transmit lock instead.

- Remove the driver specific transmit queue hashing and use
  skb_get_queue_mapping instead.

- Use netif_tx_{start|stop|wake}_queue where appropriate. We can also
  remove pr->queue_stopped and just check the queue status directly.

- Print all 16 queues in the ethtool stats.

We now enable multiqueue by default since it is a clear win on all my
testing so far.

v3:
[cascardo] fixed use_mcs parameter description
[cascardo] set ehea_ethtool_stats_keys as const

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>