Bluetooth: Controller: Fix ull_prepare_dequeue for skipped events

Fix ull_prepare_dequeue to not skip events when preempt
does not match the event in the head of the prepare queue.
The head of the prepare queue does not match when
ull_prepare_dequeue has put the head of the queue to the
last of the queue when it is calling lll_resume interface.
This happens when there is already an active event which
needs a preempt timeout to be setup and there is another
non-resume event in the pipeline which now becomes the
head. The fix ensure to restore the order of the events
if a preempt timeout was to be setup.

Currently ull_prepare_dequeue loops through all events
before stopping at the original way the queue was. This is
not efficient and is a scope for improvement in future.

This reverts commit 91781306e95c ("Revert "Bluetooth:
Controller: Fix ull_prepare_dequeue for skipped events"").

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