nrf802154: fix set_tx_power function
nrf802154: fix set_tx_power function

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