AP: Drop retransmitted auth/assoc/action frames

AP: Drop retransmitted auth/assoc/action frames

It is possible that a station device might miss an ACK for an
authentication, association, or action frame, and thus retransmit the
same frame although the frame is already being processed in the stack.
While the duplicated frame should really be dropped in the kernel or
firmware code where duplicate detection is implemented for data frames,
it is possible that pre-association cases are not fully addressed (which
is the case at least with mac80211 today) and the frame may be delivered
to upper layer stack.

In such a case, the local AP will process the retransmitted frame although
it has already handled the request, which might cause the station to get
confused and as a result disconnect from the AP, blacklist it, etc.

To avoid such a case, save the sequence control of the last processed
management frame and in case of retransmissions drop them.

Signed-off-by: Ilan Peer <ilan.peer@intel.com>