For *nix append CREAD only for ReadOnly or ReadWrite mode
For *nix append CREAD only for ReadOnly or ReadWrite mode

Change-Id: I0d6f74151977cb8a7dc5cfaf8fab5889293d54a3
Reviewed-by: Sergey Belyashov <8871b4c2d635fca691211507eadbac3d0bc2695a@gmail.com>
Reviewed-by: Denis Shienkov <1ad2dee90c89b865e4a01188e9919a005e3f77cf@yandex.ru>

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