mac80211: add HE 6 GHz capability only if supported

The HE 6 GHz capability should only be included if there
are actually available channels on 6 GHz, and if that's
the case we need to get it from the 6 GHz band data, not
whatever other band we're on now.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20210618133832.290bf5c87030.I178aff1c3a6e32456d4ac9238e4a2eb47d209ccd@changeid
Link: https://lore.kernel.org/r/iwlwifi.20210618133832.05e935e8dd98.I83ff7eb2ae8ebdf2e30c4fa2461344d9e569f599@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/util.c

@@ -6,7 +6,7 @@
  * Copyright 2007	Johannes Berg <johannes@sipsolutions.net>
  * Copyright 2013-2014  Intel Mobile Communications GmbH
  * Copyright (C) 2015-2017	Intel Deutschland GmbH
- * Copyright (C) 2018-2020 Intel Corporation
+ * Copyright (C) 2018-2021 Intel Corporation
  *
  * utilities for mac80211
  */
@@ -2960,12 +2960,15 @@ void ieee80211_ie_build_he_6ghz_cap(struct ieee80211_sub_if_data *sdata,
 	u8 *pos;
 	u16 cap;
 
-	sband = ieee80211_get_sband(sdata);
-	if (!sband)
+	if (!cfg80211_any_usable_channels(sdata->local->hw.wiphy,
+					  BIT(NL80211_BAND_6GHZ),
+					  IEEE80211_CHAN_NO_HE))
 		return;
 
+	sband = sdata->local->hw.wiphy->bands[NL80211_BAND_6GHZ];
+
 	iftd = ieee80211_get_sband_iftype_data(sband, iftype);
-	if (WARN_ON(!iftd))
+	if (!iftd)
 		return;
 
 	/* Check for device HE 6 GHz capability before adding element */