Now, MCU is able to go in stop mode if necessary when
periph_pm feature is activated.
Regarding LPSDSR bit that deactivates or not regulator in stop
mode, it is up to the user to set/clear this bit. In order
to save power, voltage regulator can be set in low power state
during stop mode but it increases wakeup time.
Signed-off-by: Aurelien Fillau <aurelien.fillau@gmail.com>
- removed neccessity to define empty `DAC_NUMOF 0` for each STM
base board
- adapted all board configs to this
- joined stm32f2 to use common DAC driver
- improved code of DAC driver
