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/net/mac80211/mlme.c b/net/mac80211/mlme.c
index a2f5e62..bfd571e 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -842,6 +842,7 @@
 		sdata->vif.bss_conf.timestamp = bss->cbss.tsf;
 		sdata->vif.bss_conf.dtim_period = bss->dtim_period;
 
+		bss_info_changed |= BSS_CHANGED_BEACON_INT;
 		bss_info_changed |= ieee80211_handle_bss_capability(sdata,
 			bss->cbss.capability, bss->has_erp_value, bss->erp_value);