cpu/cc2538/radio/Kconfig: indicate that radio HAL is implemented
cpu/cc2538/radio/Kconfig: indicate that radio HAL is implemented

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