netfilter: nf_tables: remove unneeded conditional

This helper is inlined, so keep it as small as possible.

If the static key is true, there is only a very small chance
that info->trace is false:

1. tracing was enabled at this very moment, the static key was
   updated to active right after nft_do_table was called.

2. tracing was disabled at this very moment.
   trace->info is already false, the static key is about to
   be patched to false soon.

In both cases, no event will be sent because info->trace
is false (checked in noinline slowpath). info->nf_trace is irrelevant.

The nf_trace update is redunant in this case, but this will only
happen for short duration, when static key flips.

       text  data   bss   dec   hex filename
old:   2980   192    32  3204   c84 nf_tables_core.o
new:   2964   192    32  3188   c74i nf_tables_core.o

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