netfilter: ipset: Fix nla_policies to fully support NL_VALIDATE_STRICT

Since v5.2 (commit "netlink: re-add parse/validate functions in strict
mode") NL_VALIDATE_STRICT is enabled. Fix the ipset nla_policies which did
not support strict mode and convert from deprecated parsings to verified ones.

Signed-off-by: Jozsef Kadlecsik <kadlec@netfilter.org>