iwl3945: use iwl3945_add_bcast_station

iwl3945 should not use iwl_add_local_station(..., false)
because that would leave the IWL_STA_UCODE_INPROGRESS flag
set for the station, which is not desirable. Instead it
can use iwl3945_add_bcast_station() here.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>