Expose TxPower for bluetooth devices during discovery

device/bluetooth/bluetooth_device_mac.mm

Index: device/bluetooth/bluetooth_device_mac.mm
diff --git a/device/bluetooth/bluetooth_device_mac.mm b/device/bluetooth/bluetooth_device_mac.mm
index aabe35eba6aab6ab290fca3fc84b2d5965b8629a..63da26493b2f68e401bb83fa57f05edb0e6db454 100644
--- a/device/bluetooth/bluetooth_device_mac.mm
+++ b/device/bluetooth/bluetooth_device_mac.mm
@@ -129,6 +129,11 @@ int16 BluetoothDeviceMac::GetInquiryRSSI() const {
   return kUnknownPower;
 }
 
+int16 BluetoothDeviceMac::GetInquiryTxPower() const {
+  NOTIMPLEMENTED();
+  return kUnknownPower;
+}
+
 bool BluetoothDeviceMac::ExpectingPinCode() const {
   NOTIMPLEMENTED();
   return false;