netfilter: nf_{log,queue}: fix compilation without CONFIG_PROC_FS

This patch fixes the following compilation error:

net/netfilter/nf_log.c:373:38: error: 'struct netns_nf' has no member named 'proc_netfilter'

if procfs is not set.

The netns support for nf_log, nfnetlink_log and nfnetlink_queue_core
requires CONFIG_PROC_FS in the removal path of their respective
/proc interface since net->nf.proc_netfilter is undefined in that
case.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Acked-by: Gao feng <gaofeng@cn.fujitsu.com>