remove dependence of working QSerialPortInfo
remove dependence of working QSerialPortInfo

On system with no support to QSerialPortInfo the constructor
QSerialPort(QString portName, QObject *parent) don't works.

Change-Id: I1a98e03f9153d2b963fa2985901e40ddf17717cf
Reviewed-by: Laszlo Papp <2164cc32668ec579454611fc5261234262c80421@kde.org>

RoadWorksSoftware/QtSerialPort-OS2,kobolabs/qtserialport,RoadWorksSoftware/QtSerialPort-OS2,kobolabs/qtserialport