ble_radio_notification.c correction

[JB21]

In ble_radio_notification.c

this line has to be added:

#include "nrf_nvic.h"

Otherwise one gets compilations errors for

sd_nvic_ClearPendingIRQ etc.

[MartinBL]

Thanks for reporting. It is actually already reported in our bug tracker, but it seems to have fallen through the cracks.