zfs: add missed dependency of zfs module on zlib

Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Martin Matuska <mm@FreeBSD.org>
Co-authored-by: Konstantin Belousov <kib@FreeBSD.org>
Signed-off-by: Ryan Moeller <ryan@iXsystems.com>
External-issue: https://reviews.freebsd.org/D31207
Closes #12442