netfilter: ctnetlink: be more strict when NF_CONNTRACK_MARK is not set

When CONFIG_NF_CONNTRACK_MARK is not set, any CTA_MARK or CTA_MARK_MASK
in netlink message are not supported. We should return an error when one
of them is set, not both

Fixes: 9306425b ("netfilter: ctnetlink: must check mark attributes vs NULL")
Signed-off-by: Romain Bellan <romain.bellan@wifirst.fr>
Signed-off-by: Florent Fourcot <florent.fourcot@wifirst.fr>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>