Some NRF52 boards are able to use the internal power-efficient DC/DC
regulator. Add a new class that can be inherited by board classes to
enable this feature and reduce the power consumption.
Signed-off-by: Frieder Schrempf <frieder@fris.de>
Use a common begin() method that can be called from derived classes
to contain the shared initialization code.
Signed-off-by: Frieder Schrempf <frieder@fris.de>
