Revert "sound: Implement asynchronous device detach"
This reverts commit 9eff58c6d52b66eb8abe7f724dabcd804a566df4.
We are reverting dc831e93bad6 ("sound: Get rid of snd_clone and use
DEVFS_CDEVPRIV(9)"), so revert this commit as well since it depends
dc831e93bad6.