[IPV4]: Consolidate common SNMP code

This patch moves the SNMP code shared between IPv4/IPv6 from proc.c
into net/ipv4/af_inet.c.  This makes sense because these functions
aren't specific to /proc.

As a result we can again skip proc.o if /proc is disabled.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/ip.h b/include/net/ip.h
index f41ce07..bb207db 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -166,6 +166,7 @@
 #define NET_ADD_STATS_BH(field, adnd)	SNMP_ADD_STATS_BH(net_statistics, field, adnd)
 #define NET_ADD_STATS_USER(field, adnd)	SNMP_ADD_STATS_USER(net_statistics, field, adnd)
 
+extern unsigned long snmp_fold_field(void *mib[], int offt);
 extern int snmp_mib_init(void *ptr[2], size_t mibsize, size_t mibalign);
 extern void snmp_mib_free(void *ptr[2]);