The internal DC/DC converter is more efficient compared to the LDO
regulator. The downside of the DC/DC converter is that it requires an
external inductor to be present on the board. Enabling the DC/DC
converter is guarded with NRF5X_ENABLE_DCDC, this macro must be defined
if the DC/DC converter is to be enabled.
- Removed stdio_init() from newlib's _init(), as this is too late in the boot
process to allow DEBUG()ing during periph_init()
- Added stdio_init() to the various cpu_init() routines of the ARM CPUs just
before periph_init()
Prevent CPU from using cortexm_init() when softdevice is used for NRF52 devices
as the softdevice already do some obscur inits
Also ensure the softdevice pkg will be used by hacking Makefile due to RIOT's
build system limitations (will be fix later with the new build system)
This function is supposed to be used for putting the CPU into
sleep mode for short amounts of time (e.g. in typical polling
loops used in periph drivers).
