ath9k: Remove is_bslot_active

In the tx_last_beacon() callback, mac80211's beaconing
status can be used instead. The beacon tasklet doesn't require
it because it is disabled when removing a slot.

Signed-off-by: Sujith Manoharan <c_manoha@qca.qualcomm.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 e411189..fa97fac 100644
--- a/drivers/net/wireless/ath/ath9k/main.c
+++ b/drivers/net/wireless/ath/ath9k/main.c
@@ -1788,10 +1788,11 @@
 	if (!vif)
 		return 0;
 
-	avp = (void *)vif->drv_priv;
-	if (!avp->is_bslot_active)
+	if (!vif->bss_conf.enable_beacon)
 		return 0;
 
+	avp = (void *)vif->drv_priv;
+
 	if (!sc->beacon.tx_processed && !edma) {
 		tasklet_disable(&sc->bcon_tasklet);