netfilter: nf_tables: fix crash when nf_trace is enabled

do not access info->pkt when info->trace is not 1.
nft_traceinfo is not initialized, except when tracing is enabled.

The 'nft_trace_enabled' static key cannot be used for this, we must
always check info->trace first.

Pass nft_pktinfo directly to avoid this.

Fixes: e34b9ed9 ("netfilter: nf_tables: avoid skb access on nf_stolen")
Reported-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>