netfilter: x_tables: pass xt_counters struct instead of packet counter

netfilter: x_tables: pass xt_counters struct instead of packet counter

BugLink: https://bugs.launchpad.net/bugs/1640786
On SMP we overload the packet counter (unsigned long) to contain
percpu offset.  Hide this from callers and pass xt_counters address
instead.

Preparation patch to allocate the percpu counters in page-sized batch
chunks.

Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
(backported from commit 4d31eef5176df06f218201bc9c0ce40babb41660)
Signed-off-by: Eric Desrochers <eric.desrochers@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>