drivers: clock_control: nrf: hfxo: impl zero-latency isr API

Implement the zero latency interrupt safe APIs to the HFXO clock
commonly used by the bluetooth stach from zero latency interrupt
context.

Co-authored-by: Piotr Pryga <piotr.pryga@nordicsemi.no>

Signed-off-by: Bjarki Arge Andreasen <bjarki.andreasen@nordicsemi.no>
Signed-off-by: Piotr Pryga <piotr.pryga@nordicsemi.no>