stm32f1 periph_rtc implementation gets a 1s resolution by dividing
CLOCK_LSx by 32768. This only make sense if CLOCK_LSE is set,
otherwise CLOCK_LSI=~40000, which will lead to an imprecise rtc.
The Nucleo-F103RB comes with an internal SWD programmer/debugger. Thus, the JTAG
pins are not going to be used for debugging / programming anyway. The pins are
exposed on the headers, so allowing them to be used as GPIOs make a lot of
sense.
The Bluepill / Blackpill boards only expose the SWD pins on the debug header,
but the JTAG pins (not also used by SWD) are exposed on the GPIO pin headers.
Hence, exposing them as regular GPIOs seems to be a reasonable choice.
- Created new `bluepill-128kib` as 128KiB version of the `bluepill`
- Created new `blackpill-128kib` as 128KiB version of the `blackpill`
- Updated `openocd.cfg` to allow flashing 128KiB of ROM
