cfg80211: require HE capabilities for 6 GHz band

On 6 GHz band, HE capabilities must be available for all of
the interface types, otherwise we shouldn't use 6 GHz. Check
this.

Link: https://lore.kernel.org/r/20200528213443.5881cb3c8c4a.I583b54172f91f98d44af64a16c5826fe458cbb27@changeidSigned-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/core.c

@@ -791,6 +791,7 @@ int wiphy_register(struct wiphy *wiphy)
 	/* sanity check supported bands/channels */
 	for (band = 0; band < NUM_NL80211_BANDS; band++) {
 		u16 types = 0;
+		bool have_he = false;
 
 		sband = wiphy->bands[band];
 		if (!sband)
@@ -859,8 +860,17 @@ int wiphy_register(struct wiphy *wiphy)
 				return -EINVAL;
 
 			types |= iftd->types_mask;
+
+			if (i == 0)
+				have_he = iftd->he_cap.has_he;
+			else
+				have_he = have_he &&
+					  iftd->he_cap.has_he;
 		}
 
+		if (WARN_ON(!have_he && band == NL80211_BAND_6GHZ))
+			return -EINVAL;
+
 		have_band = true;
 	}