lwtunnel: be STRICT to validate the new LWTUNNEL_IP(6)_OPTS

LWTUNNEL_IP(6)_OPTS are the new items in ip(6)_tun_policy, which
are parsed by nla_parse_nested_deprecated(). We should check it
strictly by setting .strict_start_type = LWTUNNEL_IP(6)_OPTS.

This patch also adds missing LWTUNNEL_IP6_OPTS in ip6_tun_policy.

Fixes: 4ece4778 ("lwtunnel: add options setting and dumping for geneve")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>