mac80211: clean up beacon interval settings

We currently have two beacon interval configuration knobs:
hw.conf.beacon_int and vif.bss_info.beacon_int. This is
rather confusing, even though the former is used when we
beacon ourselves and the latter when we are associated to
an AP.

This just deprecates the hw.conf.beacon_int setting in favour
of always using vif.bss_info.beacon_int. Since it touches all
the beaconing IBSS code anyway, we can also add support for
the cfg80211 IBSS beacon interval configuration easily.

NOTE: The hw.conf.beacon_int setting is retained for now due
      to drivers still using it -- I couldn't untangle all
      drivers, some are updated in this patch.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/xmit.c b/drivers/net/wireless/ath/ath9k/xmit.c
index faf2cab..501493f 100644
--- a/drivers/net/wireless/ath/ath9k/xmit.c
+++ b/drivers/net/wireless/ath/ath9k/xmit.c
@@ -971,7 +971,7 @@
 	else if (sc->config.cabqReadytime > ATH9K_READY_TIME_HI_BOUND)
 		sc->config.cabqReadytime = ATH9K_READY_TIME_HI_BOUND;
 
-	qi.tqi_readyTime = (sc->hw->conf.beacon_int *
+	qi.tqi_readyTime = (sc->beacon_interval *
 			    sc->config.cabqReadytime) / 100;
 	ath_txq_update(sc, qnum, &qi);