mac80211: ignore country element TX power on 6 GHz

Updates to the 802.11ax draft are coming that deprecate the
country element in favour of the transmit power envelope
element, and make the maximum transmit power level field in
the triplets reserved, so if we parse them we'd use 0 dBm
transmit power.

Follow suit and completely ignore the element on 6 GHz for
purposes of determining TX power.
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.20201206145305.9abf9f6b4f88.Icb6e52af586edcc74f1f0360e8f6fc9ef2bfe8f5@changeidSigned-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/mlme.c

@@ -1572,9 +1572,17 @@ ieee80211_find_80211h_pwr_constr(struct ieee80211_sub_if_data *sdata,
 		chan_increment = 1;
 		break;
 	case NL80211_BAND_5GHZ:
-	case NL80211_BAND_6GHZ:
 		chan_increment = 4;
 		break;
+	case NL80211_BAND_6GHZ:
+		/*
+		 * In the 6 GHz band, the "maximum transmit power level"
+		 * field in the triplets is reserved, and thus will be
+		 * zero and we shouldn't use it to control TX power.
+		 * The actual TX power will be given in the transmit
+		 * power envelope element instead.
+		 */
+		return false;
 	}
 
 	/* find channel */