rtlwifi: Update beacon statistics for USB driver

The USB drivers were not updating the beacon statistics, which led to
false beacon loss indications.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Stable <stable@vger.kernel.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rtlwifi/usb.c

@@ -481,6 +481,8 @@ static void _rtl_usb_rx_process_agg(struct ieee80211_hw *hw,
 			if (unicast)
 				rtlpriv->link_info.num_rx_inperiod++;
 		}
+		/* static bcn for roaming */
+		rtl_beacon_statistic(hw, skb);
 	}
 }