mlx4: Fixing Ethernet unicast packet steering

For older FW versions, fixing the usage of per port Mac table.
For each port we must define the base QP number, which is passed
to the HW.
Setting the correct value in SET_PORT FW command to enable the steering.

Reported-by: Roland Dreier <roland@purestorage.com>
Tested-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
Signed-off-by: David S. Miller <davem@davemloft.net>