serial_port not accepting all the baud rates as an option

[mrbahrani]

Using serial port object, I wanted to send some bytes to a firmware that accepted a connection with the baud rate of 1500000 which is an unconventional value for the baud rate. My program terminated as error was thrown from calling .set_option method, with this baud rate, from serial_port object.
I tried to dig deeper into the error as I figured out struct termios is used for all the Unix systems, that treats baud rate value as an enum value with only standard baud rates while for Linux, there also exists struct termios2 that accepts the baud rate as an unsigned integer. Potentially, QSerialPort has used this struct as I didn't have such problem with that. I'm available to add the option of using termios2 when available to solve this problem.