mac80211: use oper_channel in utils and config

Using hw.conf.channel is wrong as it could be the
temporary channel if any function like the beacon
get function is called while scanning or during
other temporary out-of-channel activities.

Use oper_channel instead.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index bfb57dc..fc8ba83 100644
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -1274,7 +1274,7 @@
 	/* reset some values that shouldn't be kept across type changes */
 	sdata->vif.bss_conf.basic_rates =
 		ieee80211_mandatory_rates(sdata->local,
-			sdata->local->hw.conf.channel->band);
+			sdata->local->oper_channel->band);
 	sdata->drop_unencrypted = 0;
 	if (type == NL80211_IFTYPE_STATION)
 		sdata->u.mgd.use_4addr = false;