Handle the ERROR_INVALID_NAME error code

If the user tries to open the serial port with empty
port name, Windows returns this error code.

The error will be exposed as
QSerialPort::DeviceNotFoundError from now.

Tested only on Windows 8 (32 bit) with on-board serial
port as well as an usb dongle (PL2303) using Qt4 and Qt5.

Change-Id: I9a56a7e51dbdab684b6d2a9fdf6398d8d5018e1c
Reviewed-by: Laszlo Papp <lpapp@kde.org>
Reviewed-by: Sergey Belyashov <Sergey.Belyashov@gmail.com>