unicode: Don't special case ignorable code points

commit 5c26d2f1 upstream.

We don't need to handle them separately. Instead, just let them
decompose/casefold to themselves.

Signed-off-by: Gabriel Krisman Bertazi <krisman@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>