mac80211: update new sta's rx timestamp

This patch fixes needless probe request caused by zero value in
sta->last_rx inside ieee80211_associated flow

Signed-off-by: Ron Rindjunsky <ron.rindjunsky@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/mlme.c

@@ -2103,6 +2103,8 @@ static void ieee80211_rx_mgmt_assoc_resp(struct ieee80211_sub_if_data *sdata,
 			rcu_read_unlock();
 			return;
 		}
+		/* update new sta with its last rx activity */
+		sta->last_rx = jiffies;
 	}
 
 	/*