From: Andrey Borzenkov <arvidjaar@mail.ru>

A while back Andrey fixed a devfs bug in which we were running
remove_wait_queue() against a wait_queue_head which was on another process's
stack, and which had gone out of scope.

The patch reverts that fix and does it the same way as 2.4: just leave the
waitqueue struct dangling on the waitqueue_head: there is no need to touch it
at all.

It adds a big comment explaining why we are doing this nasty thing.