ft: netdev: refactor FT-over-DS into two stages

FT-over-DS followed the same pattern as FT-over-Air which worked,
but really limited how the protocol could be used. FT-over-DS is
unique in that we can authenticate to many APs by sending out
FT action frames and parsing the results. Once parsed IWD can
immediately Reassociate, or do so at a later time.

To take advantage of this IWD need to separate FT-over-DS into
two stages: action frame and reassociation.

The initial action frame stage is started by netdev. The target
BSS is sent an FT action frame and a new cache entry is created
in ft.c. Once the response is received the entry is updated
with all the needed data to Reassociate. To limit the record
keeping on netdev each FT-over-DS entry holds a userdata pointer
so netdev doesn't need to maintain its own list of data for
callbacks.

Once the action response is parsed netdev will call back signalling
the action frame sequence was completed (either successfully or not).
At this point the 'normal' FT procedure can start using the
FT-over-DS auth-proto.
4 files changed