Fix to use serial with 8 data bits and parity

In the development of a driver for a gps who uses odd parity with 8 data bits, I configured the serial to use 8 data bits and odd parity on gps_helper.cpp (*.c_cflag) the result was 7 data bits and my 8th data bit used to parity... My fix switch the word length to 9 data bits (just when we want parity) on stm32 and the final result is 8 data bits + parity bit as expected.