ath9k: Remove redundant beacon_interval

The variable appears in both ath_softc and ath_beacon_config.
The struct ath_beacon_config is embedded in ath_softc. The redundant
variable was added by commit id 57c4d7b4c4986037be51476b8e3025d5ba18d8b8.

Signed-off-by: Steve Brown <sbrown@cortland.com>
Reviewed-by: Mohammed Shafi <shafi.ath9k@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/main.c b/drivers/net/wireless/ath/ath9k/main.c
index 12e0ac6..8469d7c 100644
--- a/drivers/net/wireless/ath/ath9k/main.c
+++ b/drivers/net/wireless/ath/ath9k/main.c
@@ -1891,6 +1891,7 @@
 				   u32 changed)
 {
 	struct ath_softc *sc = hw->priv;
+	struct ath_beacon_config *cur_conf = &sc->cur_beacon_conf;
 	struct ath_hw *ah = sc->sc_ah;
 	struct ath_common *common = ath9k_hw_common(ah);
 	struct ath_vif *avp = (void *)vif->drv_priv;
@@ -1949,7 +1950,7 @@
 		ath9k_hw_stoptxdma(sc->sc_ah, sc->beacon.beaconq);
 
 	if (changed & BSS_CHANGED_BEACON_INT) {
-		sc->beacon_interval = bss_conf->beacon_int;
+		cur_conf->beacon_interval = bss_conf->beacon_int;
 		/*
 		 * In case of AP mode, the HW TSF has to be reset
 		 * when the beacon interval changes.