iwl3945: cleanup number of queues settings

* Rename maximum number of queue (TFD_QUEUE_MAX) to IWL39_NUM_QUEUES to
  be consistent with rest of iwlwifi.
* Remove unused defines.
* Fix loops that iterate over number of TX queues to stop when maximum is reached
  (currently it is maximum + 1).
* Remove queues_num module parameter as it is not used.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>