mac80211: add TDLS connection timeout

Adding a timeout for tearing down a TDLS connection that
hasn't had ACKed traffic sent through it for a certain
amount of time.

Since we have no other monitoring facility to indicate the
existance (or non-existance) of a peer, this patch will
cause a peer to be considered as unavailable if for some X
time at least some Y packets have all not been ACKed.

Signed-off-by: Liad Kaufman <liad.kaufman@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/sta_info.h

@@ -450,6 +450,9 @@ struct sta_info {
 	enum ieee80211_smps_mode known_smps_mode;
 	const struct ieee80211_cipher_scheme *cipher_scheme;
 
+	/* TDLS timeout data */
+	unsigned long last_tdls_pkt_time;
+
 	/* keep last! */
 	struct ieee80211_sta sta;
 };