Fix for issue #4452 - time.sleep on STM

[DavePutz]

Issue #4452. In stm32_peripherals_rtc_set_alarm(), if the STM chip has a high-speed crystal, the value of rtc_clock_frequency is 32000. The SubSeconds calculation in line 185, however, will overflow whenever (raw_ticks % TICK_DIVISOR) is > 1000. The multiplication by 32 will give a value > rtc_clock_frequency. Since alarm.AlarmTime.SubSeconds is an unsigned 32-bit int, the result will wrap around and the sub-seconds time calculation will be very incorrect. The fix is to adjust the calculation by adding rtc_clock_frequency back to SubSeconds if the calculation has wrapped.
Note that a possibly related issue at line 89 in stm32_peripherals_rtc_init() could have resulted in an extended loop, the "while" has been changed to an "if" to make sure that no more than two reads of the SSR take place.
Testing with the script from issue #4452 gives the following output:

Adafruit CircuitPython 7.3.0-beta-1-dirty on 2022-04-21; STM32F411E_DISCO with STM32F411xE
93.186
2.53702
2.561
2.53699
2.56
2.53702
2.56097
2.561
2.53702
2.56
2.53699
2.561
2.53702
2.56097

Which is much improved over the initally reported results.

[dhalbert]

Thank you for this fix!