btrfs: call fsnotify_rmdir() hook

This will allow generating fsnotify delete events after the
fsnotify_nameremove() hook is removed from d_delete().

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Acked-by: David Sterba <dsterba@suse.com>
Signed-off-by: Jan Kara <jack@suse.cz>