DebugFS : file/directory removal fix

Fix file and directory removal in debugfs. Add inotify support for file removal.

The following scenario :
create dir a
create dir a/b

cd a/b (some process goes in cwd a/b)

rmdir a/b
rmdir a

fails due to the fact that "a" appears to be non empty. It is because
the "b" dentry is not deleted from "a" and still in use. The same
problem happens if "b" is a file. d_delete is nice enough to know when
it needs to unhash and free the dentry if nothing else is using it or,
if someone is using it, to remove it from the hash queues and wait for
it to be deleted when it has no users.

The nice side-effect of this fix is that it calls the file removal
notification.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>