IB/mlx4: Add support for extended counters over RoCE ports

When attribute IB_PMA_PORT_COUNTERS_EXT is set, we now return 64 bit
values for the counters.

Signed-off-by: Eran Ben Elisha <eranbe@mellanox.com>
Signed-off-by: Matan Barak <matanb@mellanox.com>
Reviewed-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>