suspend-on-idle: use earlier (safer) hooks for stream unlink notifications

suspend-on-idle: use earlier (safer) hooks for stream unlink notifications

In the "unlink post" hook it's not guaranteed that the stream's old
device exists any more, so let's use the "unlink" hook that is safer.
For example, module-bluetooth-policy does a card profile change in the
source-output "unlink post" hook, which invalidates the source-output's
source pointer.

When the "unlink" hook is fired, the stream is still linked to its
device, which affects the return values of the check_suspend()
functions. The unlinked streams should be ignored by the check_suspend()
functions, so I had to add extra parameters to those functions.