hostapd: add interworking support
This adds configuration options to enable interworking for hostapd.
All options require iw_enabled to be set to 1 for a given VAP.
All IEEE802.11u related settings are supported with exception of the
venue information which will be added as separate UCI sections at a
later point.
The options use the same name as the ones from the hostapd.conf file
with a "iw_" prefix added.
All UCI configuration options are passed without further modifications
to hostapd with exceptions of the following options, whose elements can
be provided using UCI lis elements:
- iw_roaming_consortium
- iw_anqp_elem
- iw_nai_realm
- iw_domain_name
- iw_anqp_3gpp_cell_net
Signed-off-by: David Bauer <mail@david-bauer.net>