drivers: timer: stm32 lptim: add support for backup standby timer

Add support for a backup standby timer in STM32 LPTIM driver for cases
when the LPTIM is not available (ie standby low power mode).
A counter (typically RTC) is used for such a case.

Signed-off-by: Guillaume Gautier <guillaume.gautier-ext@st.com>
2 files changed