net/mlx4_en: Moderate ethtool callback to show more statistics

More packet statistics are now calculated and visible to the user via
ethtool:

- RX packet errors statistics.
- TX/RX drops are now calculated.
- TX multicast and broadcast statistics.
- RX/TX per priority bytes statistics.
- RX/TX no vlan packets and bytes statistics.

Signed-off-by: Eran Ben Elisha <eranbe@mellanox.com>
Signed-off-by: Hadar Hen Zion <hadarh@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>