iwlwifi: rename iwl_add_local_station

This function is now only used for the special
IBSS BSSID station, so rename it to indicate
this. The new name is iwl_add_bssid_station.

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