netfilter: nf_tables: fix nf_log_trace based tracing

nf_log_trace() outputs bogus 'TRACE:' strings because I forgot to update
the comments array.

Fixes: 33d5a7b1 ("netfilter: nf_tables: extend tracing infrastructure")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>