mac80211: Extend SAE authentication in infra BSS STA mode

Previous implementation of SAE authentication in infrastructure BSS was
somewhat restricting and not exactly clean way of handling the two
auth() operations. This ended up removing and re-adding the STA entry
for the AP in the middle of authentication and also messing up
authentication state tracking through the sequence of four
Authentication frames. Furthermore, this did not work if the AP ended up
sending out SAE Confirm (auth trans #2) immediately after SAE Commit
(auth trans #1) before the station had time to transmit its SAE Confirm.

Clean up authentication state handling for the SAE case to allow two
rounds of auth() calls without dropping all state between those
operations. Track peer Confirmed status and mark authentication
completed only once both ends have confirmed.

ieee80211_mgd_auth() check for EBUSY cases is now handling only the
pending association (ifmgd->assoc_data) while all pending authentication
(ifmgd->auth_data) cases are allowed to proceed to allow user space to
start a new connection attempt from scratch even if the previously
requested authentication is still waiting completion. This is needed to
avoid making SAE error cases with retries take excessive amount of time
with no means for the user space to stop that (apart from setting the
netdev down).

As an extra bonus, the end of ieee80211_rx_mgmt_auth() can be cleaned up
to avoid the extra copy of the cfg80211_rx_mlme_mgmt() call for ongoing
SAE authentication since the new ieee80211_mark_sta_auth() helper
function can handle both completion of authentication and updates to the
STA entry under the same condition and there is no need to return from
the function between those operations.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>