Note that this could have side effects on the application as it would
not be aware that data has been missed. This may be later solved by
adding an error management parameter to the Serial API in mbed.
The advantage is that the serial link can work again.
Reworked the serial_format() function for STM32F0x
devices to take the format in the form:
data_bits - parity - stop_bits
E.g. 8 - N - 1
where data_bits exclude the parity bit.
Added a case for 7 bits data as at least the chips
STM32F0x1/STM32F0x2/STM32F0x8 support 7 bits data.
Consolidated serial_format() and uart_init()
functions into a general TARGET_STM serial_api.c
file since the functions are common to all STM targets.
Fixes#4189