[NET]: Protect neigh_stat_seq_fops by CONFIG_PROC_FS

From: Amos Waterland <apw@us.ibm.com>

If CONFIG_PROC_FS is not selected, the compiler emits this warning:

 net/core/neighbour.c:64: warning: `neigh_stat_seq_fops' defined but not used

Which is correct, because neigh_stat_seq_fops is in fact only
initialized and used by code that is protected by CONFIG_PROC_FS.  So
this patch fixes that up.

Signed-off-by: Amos Waterland <apw@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>