cpu/nrf5x_common/periph_temperature: Increase resolution
cpu/nrf5x_common/periph_temperature: Increase resolution

Modify the periph_temperature implementation to expose the full
resolution of the temperature sensor. The accuracy of the sensor will
likely be less than 0.25 °C, but typically temperature sensors have
a precision in the order of their resolution. Exposing the full
resolution can therefore be useful to monitor relative temperature
changes.

kYc0o/RIOT,miri64/RIOT,jasonatran/RIOT,miri64/RIOT,ant9000/RIOT,ant9000/RIOT,jasonatran/RIOT,ant9000/RIOT,jasonatran/RIOT,miri64/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,RIOT-OS/RIOT,ant9000/RIOT,miri64/RIOT,kaspar030/RIOT,kaspar030/RIOT,kYc0o/RIOT,kYc0o/RIOT,kaspar030/RIOT,kYc0o/RIOT,RIOT-OS/RIOT,OlegHahm/RIOT,ant9000/RIOT,OlegHahm/RIOT,kYc0o/RIOT,miri64/RIOT,OlegHahm/RIOT,jasonatran/RIOT,jasonatran/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,OlegHahm/RIOT,OlegHahm/RIOT,RIOT-OS/RIOT