iwlwifi: W/A for the TSF correction in IBSS

This patch is a W/A for the TSF sync issue in IBSS merging. HW is not
capable to sync TSF (it's constantly little behind). This creates
constant IBSS merging upon reception of each beacon, adding and removing
station which in turn creates above 50% packet loss and thus dramatically
degrade the throughput. The W/A simply stops the driver from declaring it
has a reliable TSF value and thus eliminates IBSS merging.

Signed-off-by: Assaf Krauss <assaf.krauss@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-agn.c

@@ -3588,7 +3588,7 @@ static int iwl4965_mac_beacon_update(struct ieee80211_hw *hw, struct sk_buff *sk
 
 	priv->assoc_id = 0;
 	timestamp = ((struct ieee80211_mgmt *)skb->data)->u.beacon.timestamp;
-	priv->timestamp = le64_to_cpu(timestamp) +  (priv->beacon_int * 1000);
+	priv->timestamp = le64_to_cpu(timestamp);
 
 	IWL_DEBUG_MAC80211("leave\n");
 	spin_unlock_irqrestore(&priv->lock, flags);

drivers/net/wireless/iwlwifi/iwl-rx.c

@@ -1173,7 +1173,10 @@ void iwl_rx_reply_rx(struct iwl_priv *priv,
 
 	rx_status.antenna = 0;
 	rx_status.flag = 0;
-	rx_status.flag |= RX_FLAG_TSFT;
+
+	/* TSF isn't reliable. In order to allow smooth user experience,
+	 * this W/A doesn't propagate it to the mac80211 */
+	/*rx_status.flag |= RX_FLAG_TSFT;*/
 
 	if ((unlikely(rx_start->cfg_phy_cnt > 20))) {
 		IWL_DEBUG_DROP("dsp size out of range [0,20]: %d/n",