netfilter: nf_tables: remove old nf_log based tracing

nfnetlink tracing is available since nft 0.6 (June 2016).
Remove old nf_log based tracing to avoid rule counter in main loop.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>