IB/mlx5: Refactor code for counters allocation

To support per device counters in switchdev mode (instead of
per port counter), refactor query routines to work on mlx5_ib_counter
structure instead of mlx5_ib_port structure.

Signed-off-by: Parav Pandit <parav@mellanox.com>
Reviewed-by: Daniel Jurgens <danielj@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Link: https://lore.kernel.org/r/20190723073117.7175-2-leon@kernel.org


Signed-off-by: Doug Ledford <dledford@redhat.com>