Notifiers shouldn't run in the caller's context when triggered on the same core

[lyakh]

Describe the bug notifier_event() is supposed to send notifications to all registered listeners. When the listener is on a different core, its callback is called in the IDC thread context, but if it's on the same core, it runs directly in the caller's context, which is inconsistent and can block high priority contexts for prolonged periods of time.

Expected behavior When running on the same core, notification callbacks should run in an asynchronous (potentially low priority) context.

Impact https://github.com/thesofproject/sof/pull/10177#discussion_r2332503956

[lgirdwood]

I think we can fix this over time with RTIO do deal with cross core and memory domain notify producers and consumers.