Bluetooth: Controller: Fix leak in scheduled ticker node

Fix leak in scheduled ticker node when rescheduling ticker
nodes.

Applications having active Extended Advertising or Observer
role with the use of ticker reschedule in window feature
would experience assertion check failure due to delayed
radio event preparation or stalled controller with no active
roles.

Fix updating of the ticker linked list when handling
rescheduled tickers.

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