netfilter: x_tables: fix int overflow in xt_alloc_table_info()

syzkaller triggered OOM kills by passing ipt_replace.size = -1
to IPT_SO_SET_REPLACE. The root cause is that SMP_ALIGN() in
xt_alloc_table_info() causes int overflow and the size check passes
when it should not. SMP_ALIGN() is no longer needed leftover.

Remove SMP_ALIGN() call in xt_alloc_table_info().

Reported-by:  <syzbot+4396883fa8c4f64e0175@syzkaller.appspotmail.com>
Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>