mac80211: don't require VHT elements for HE on 2.4 GHz

After the previous similar bugfix there was another bug here,
if no VHT elements were found we also disabled HE. Fix this to
disable HE only on the 5 GHz band; on 6 GHz it was already not
disabled, and on 2.4 GHz there need (should) not be any VHT.

Fixes: 57fa5e8 ("mac80211: determine chandef from HE 6 GHz operation")
Link: https://lore.kernel.org/r/20201013140156.535a2fc6192f.Id6e5e525a60ac18d245d86f4015f1b271fce6ee6@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/mlme.c

@@ -5464,6 +5464,7 @@ int ieee80211_mgd_assoc(struct ieee80211_sub_if_data *sdata,
 			struct cfg80211_assoc_request *req)
 {
 	bool is_6ghz = req->bss->channel->band == NL80211_BAND_6GHZ;
+	bool is_5ghz = req->bss->channel->band == NL80211_BAND_5GHZ;
 	struct ieee80211_local *local = sdata->local;
 	struct ieee80211_if_managed *ifmgd = &sdata->u.mgd;
 	struct ieee80211_bss *bss = (void *)req->bss->priv;
@@ -5616,7 +5617,7 @@ int ieee80211_mgd_assoc(struct ieee80211_sub_if_data *sdata,
 	if (vht_ie && vht_ie[1] >= sizeof(struct ieee80211_vht_cap))
 		memcpy(&assoc_data->ap_vht_cap, vht_ie + 2,
 		       sizeof(struct ieee80211_vht_cap));
-	else if (!is_6ghz)
+	else if (is_5ghz)
 		ifmgd->flags |= IEEE80211_STA_DISABLE_VHT |
 				IEEE80211_STA_DISABLE_HE;
 	rcu_read_unlock();