drivers: clock_control: nrf: Allow calibration disabling
drivers: clock_control: nrf: Allow calibration disabling

Allow to disable calibration even though RC is used.

Signed-off-by: Krzysztof Chruscinski <9b6dc988558c51b0405b49b55c8e66862969844b@nordicsemi.no>

Vudentz/zephyr,galak/zephyr,nashif/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,Vudentz/zephyr,finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,nashif/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,Vudentz/zephyr,nashif/zephyr,Vudentz/zephyr,nashif/zephyr,Vudentz/zephyr,nashif/zephyr