net/mlx5: Lag, use hash when in roce lag on 4 ports

Downstream patches will add support for lag over 4 ports.
In that mode we will only use hash as the uplink selection method.
Using hash instead of queue affinity (before this patch) offers key
advantages like:

- Align ports selection method with the method used by the bond device

- Better packets distribution where a single queue can transmit from
  multiple ports (with queue affinity a queue is bound to a single port
  regardless of the packet being sent).

- In case of failover we traffic is split between multiple ports and not
  a single one like in queue affinity.

Going forward it was decided that queue affinity will be deprecated
as using hash provides a better user experience which means on 4 ports
HCAs hash will always be used.

Future work will add hash support for 2 ports HCAs as well.

Signed-off-by: Mark Bloch <mbloch@nvidia.com>
Reviewed-by: Maor Gottlieb <maorg@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>