Sometimes the best results (on small systems) are obtained if boot loader
leaves the CPU as it found it out of reset.
If you think in terms of an OOD life cycle: The "Destructor" for each block
reset the HW to the reset state.
With this approach, the SoC out of reset, and executing at __start from the
bootloader are 100% documented by the information the data sheet and the
reference manual.
You would still need to disable the UART in the STM32 code in order to
re-configure partity (and maybe other planners). So the solution is in
stm32_lowputc.c, not in the bootloader.
