netfilter: nf_tables: do not store verdict in traceinfo structure

Just pass it as argument to nft_trace_notify. Stack is reduced by 8 bytes:

nf_tables_core.c:256 nft_do_chain    312     static

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