/*
* tmpfs_dir_detach: disassociate directory entry and its inode,
* and detach the entry from the directory, specified by vnode.
*
* => Decreases link count on the associated node.
* => Decreases the link count on directory node, if our node is VDIR.
* => Triggers kqueue events here.
*
* => Note: dvp and vp may be NULL only if called by tmpfs_unmount().
*/