QBluetoothServiceDiscoveryAgent should have a constructor taking a QBluetoothDeviceInfo

Currently QBluetoothServiceDiscoveryAgent can be optionally started with a QBluetoothAddress parameter to limit the service discovery to one device/address.
When operating in this manner, the serviceDiscovered(const QBluetoothServiceInfo& info) signal carries an incomplete 'info' obj
(e.g. info.device().name() will return an empty string).
This doesn't happen when QBluetoothServiceDiscoveryAgent is started without the QBluetoothAddress - info.device().name() will be correctly assigned.

A common use case is to use a QBluetoothServiceDiscoveryAgent only for specific/selected results from a previous QBluetoothDeviceDiscoveryAgent. In this scenario, passing QBluetoothDeviceInfo to QBluetoothServiceDiscoveryAgent's constructor would be logical and would prevent this "information loss".

Adding a minimal patch.