net/mlx4_en: clear some TX ring stats in mlx4_en_clear_stats()

mlx4_en_clear_stats() clears about everything but few TX ring
fields are missing :
- queue_stopped, wake_queue, tso_packets, xmit_more

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Cc: Eugenia Emantayev <eugenia@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>