ath: add last_rssi to ath_common

we need access to this variable from common functions.
Signed-off-by: Oleksij Rempel <linux@rempel-privat.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath.h

@@ -161,6 +161,8 @@ struct ath_common {
 	bool btcoex_enabled;
 	bool disable_ani;
 	bool bt_ant_diversity;
+
+	int last_rssi;
 };
 
 struct sk_buff *ath_rxbuf_alloc(struct ath_common *common,