mt76: Enable NL80211_EXT_FEATURE_CQM_RSSI_LIST

Enable the use of CQM_RSSI_LIST with mt76-devices. The change has been
tested with the mt7602, mt7603 and mt7621 PCI wifi-cards. I passed a
list of RSSI thresholds to the driver, and when disconnecting/connecting
the antenna(s) I got an event each time the RSSI went above/below a
threshold.

While I have not been able to test the change with any of the mt76
USB-devices (no access to a device), the RX RSSI management code is
shared between the two device types. Thus, CQM should also work with the
mt76 USB-devices.
Signed-off-by: Kristian Evensen <kristian.evensen@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/mediatek/mt76/mac80211.c

@@ -306,6 +306,8 @@ int mt76_register_device(struct mt76_dev *dev, bool vht,
 
 	wiphy->features |= NL80211_FEATURE_ACTIVE_MONITOR;
 
+	wiphy_ext_feature_set(wiphy, NL80211_EXT_FEATURE_CQM_RSSI_LIST);
+
 	wiphy->available_antennas_tx = dev->antenna_mask;
 	wiphy->available_antennas_rx = dev->antenna_mask;