CONFIG_IWDG_STM32_TIMEOUT allowed values of 100 us for initial watchdog
timeout, which was actually rounded to zero in the driver, which uses
milliseconds resolution for timeouts. This resulted in the reload value
being set to maximum possible (calculation: 0U - 1).
This commit updates the calculation of timeout minimum and maximum
values considering the actual LSI frequency of the used MCU.
As the resolution of CONFIG_IWDG_STM32_TIMEOUT in microseconds doesn't
make sense if the driver supports only milliseconds, it is renamed to
IWDG_STM32_INITIAL_TIMEOUT (this prevents accidental wrong settings in
existing firmware) and the unit is changed to ms.
Signed-off-by: Martin Jäger <martin@libre.solar>
916dd0f6c4