Bluetooth: controller: Fix hang on directed adv timeout

During testing it was discovered that directed advertising
timeout is missing implementation to handle the timeout
happening while next event is already in preparation.
The consequence was that after the event ticker expired,
the counter is shutdown, stalling the setup PPI from
starting the erroneous advertising, leaving the controller
in an invalid hung state.

This has been fixed by correctly handling the cases, stop
between prepare and event, and stop inside radio advertising
event. The fix takes care of putting the radio active
callback and HF clock in the correct states.

Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no>