netfilter: nf_log: handle NFPROTO_INET properly in nf_logger_[find_get|put]

When we request NFPROTO_INET, it means both NFPROTO_IPV4 and NFPROTO_IPV6.

Signed-off-by: Liping Zhang <liping.zhang@spreadtrum.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>