IB/mlx5: Add per port counters

In order to support statistics for ports, we attach
each QP to a counter set which is dedicate to this port.

Signed-off-by: Mark Bloch <markb@mellanox.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>