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: NHerbert Xu <herbert@gondor.apana.org.au>
Acked-by: NYOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>