mac80211: conditionally advertise HE in probe requests

While building probe requests, only enable HE capability if
there are actually any channels in the band with HE enabled,
otherwise we're not really capable. We're doing the same in
association requests, so doing it here makes it consistent.

This also makes HE not appear available if it isn't due to
regulatory constraints.

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.b5513f2af335.Ic01862678712ae4238cea43ad2185928865efad2@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/util.c

@@ -1939,7 +1939,9 @@ static int ieee80211_build_preq_ies_band(struct ieee80211_sub_if_data *sdata,
 
 	he_cap = ieee80211_get_he_iftype_cap(sband,
 					     ieee80211_vif_type_p2p(&sdata->vif));
-	if (he_cap) {
+	if (he_cap &&
+	    cfg80211_any_usable_channels(local->hw.wiphy, BIT(sband->band),
+					 IEEE80211_CHAN_NO_HE)) {
 		pos = ieee80211_ie_build_he_cap(pos, he_cap, end);
 		if (!pos)
 			goto out_err;