Bluetooth: Controller: Fix missing auxiliary context done event

Fix missing use of auxiliary context to generate done event
which caused leak in release of auxiliary context being not
release when reference count that should decrease to zero.

Regression in 'commit 665a8d2c ("Bluetooth: Controller:
Fix repeated per sync drift compensations").

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