mac80211: simplify and improve HT/VHT/HE disable code

Check early on that a device has support for QoS (at least 4
queues) when it supports HT/VHT/HE, so we don't have to check
this while connecting.

This lets us clean up the code there: move some of it into
channel preparation to clean up a bit more, and then change
the logic to only check the "wmm_used" flag.

Additionally, disable HE consistently when VHT is disabled.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/20200131111300.891737-3-luca@coelho.fi
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/main.c

@@ -981,6 +981,11 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
 		if (!supp_he)
 			supp_he = !!ieee80211_get_he_sta_cap(sband);
 
+		/* HT, VHT, HE require QoS, thus >= 4 queues */
+		if (WARN_ON(local->hw.queues < IEEE80211_NUM_ACS &&
+			    (supp_ht || supp_vht || supp_he)))
+			return -EINVAL;
+
 		if (!sband->ht_cap.ht_supported)
 			continue;