mac80211: fix an issue in ieee80211_tx_info count field management

I noticed a possible issue in the status count field management of the
ieee80211_tx_info data structure. In particular, when the AGGR
processing is employed,
status.rates[].count is set just for the first frame and not for
others belonging to the same burst, leading to wrong statistic data in
the mac80211 debug file system.
Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi83@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/status.c

@@ -355,7 +355,13 @@ void ieee80211_tx_status(struct ieee80211_hw *hw, struct sk_buff *skb)
 	int rtap_len;
 
 	for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
-		if (info->status.rates[i].idx < 0) {
+		if ((info->flags & IEEE80211_TX_CTL_AMPDU) &&
+		    !(info->flags & IEEE80211_TX_STAT_AMPDU)) {
+			/* just the first aggr frame carry status info */
+			info->status.rates[i].idx = -1;
+			info->status.rates[i].count = 0;
+			break;
+		} else if (info->status.rates[i].idx < 0) {
 			break;
 		} else if (i >= hw->max_report_rates) {
 			/* the HW cannot have attempted that rate */