Expose TxPower for bluetooth devices during discovery

device/bluetooth/bluetooth_low_energy_device_mac.mm

Index: device/bluetooth/bluetooth_low_energy_device_mac.mm
diff --git a/device/bluetooth/bluetooth_low_energy_device_mac.mm b/device/bluetooth/bluetooth_low_energy_device_mac.mm
index e7dc1af1652ed24089e06f501ca1099635d5896b..0357ad95276aca951b3d3a10d7032ff4c230c32f 100644
--- a/device/bluetooth/bluetooth_low_energy_device_mac.mm
+++ b/device/bluetooth/bluetooth_low_energy_device_mac.mm
@@ -147,6 +147,11 @@ int16 BluetoothLowEnergyDeviceMac::GetInquiryRSSI() const {
   return kUnknownPower;
 }
 
+int16 BluetoothLowEnergyDeviceMac::GetInquiryTxPower() const {
+  NOTIMPLEMENTED();
+  return kUnknownPower;
+}
+
 bool BluetoothLowEnergyDeviceMac::ExpectingPinCode() const {
   return false;
 }