RDMA/mlx5: Delete Q counter allocations command

Remove mlx5_ib implementation of Q counter allocation logic
together with cleaning boolean which controlled validity of the
counter. It is not needed, because counter_id == 0 means that
counter is not valid.

Reviewed-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>