iwlwifi: Add tx_ant_num hw setting variable

Added tx_ant_num variable into hw_setting
This will be used for scanning TX antenna toggling
On the way removed ac_queue_num unused

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>