Bluetooth: Controller: Fix missing supervision/sync lost

When radio event prepare is cancelled due to preemption by
overlapping radio events, the extra done event processing
was missing and hence the use of accumulated prepares'
skip/latency count.
This caused the check for supervision timeout and sync
lost not be aware of the elapsed events.

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