mac80211: Adjust SAE authentication timeout

The IEEE P802.11-REVmd D1.0 specification updated the SAE authentication
timeout to be 2000 milliseconds (see dot11RSNASAERetransPeriod). Update
the SAE timeout setting accordingly.

While at it, reduce some code duplication in the timeout configuration.

Signed-off-by: Ilan Peer <ilan.peer@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>