netfilter: xtables: fix typo causing some targets not to load on IPv6

- There is no NFPROTO_IPV6 family for mark and NFLOG.
- TRACE is also missing module autoload with NFPROTO_IPV6.

This results in ip6tables failing to restore a ruleset. This issue has been
reported by several users providing incomplete patches.

Very similar to Ilya Katsnelson's patch including a missing chunk in the
TRACE extension.

Fixes: 0bfcb7b7 ("netfilter: xtables: avoid NFPROTO_UNSPEC where needed")
Reported-by: Ignat Korchagin <ignat@cloudflare.com>
Reported-by: Ilya Katsnelson <me@0upti.me>
Reported-by: Krzysztof Olędzki <ole@ans.pl>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>