Interworking: Add support for configuring arbitrary ANQP-elements

Interworking: Add support for configuring arbitrary ANQP-elements

The new hostapd configuration parameter anqp_elem can now be used to
configure arbitrary ANQP-elements for the GAS/ANQP server. In addition
to supporting new elements, this can be used to override previously
supported elements if some special values are needed (mainly for testing
purposes).

The parameter uses following format:
anqp_elem=<InfoID>:<hexdump of payload>

For example, AP Geospatial Location ANQP-element with unknown location:
anqp_elem=265:0000
and AP Civic Location ANQP-element with unknown location:
anqp_elem=266:000000

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>