The firmware clears default WEP keys on
transitions to !associated, so we need
to restore them just like stations. This
is rather implicit as part of sending a
station right now, which is odd. Make it
explicit instead and only for agn since
3945 doesn't use hw crypto for WEP.

Due to that, iwl_send_static_wepkey_cmd
is now only used in iwl-sta.c and can be
static.

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