TARGET_STM astyle

STM32 uart: update after code review

STM32 UART init update ...

- serial_init, serial_free and serial_baud function moved from serial_device.c (specific to each STM32 family) to serial_api.c (common STM32 file)
- default baudrate value was hardcoded to 9600
  - Value is set now to MBED_CONF_PLATFORM_STDIO_BAUD_RATE for STDIO
  - Value is set now to MBED_CONF_PLATFORM_DEFAULT_SERIAL_BAUD_RATE for other use
- UART init will not be stopped before calling serial_baud function

STM32s Serial does not properly handle parity bits ...

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