mac80211: dont try to use existing sta for AP

Clean out some cruft that could use an already existing
sta_info struct -- that case cannot happen. Also, there's
a bug there -- if allocation/insertion fails then it is
possible that we are left in a lingering state where
mac80211 waits for the AP, cfg80211 waits for mac80211,
but the AP has already replied. Since there's no way to
indicate an internal error, pretend there was a timeout,
i.e. that the AP never responded.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>