[IPV4]: Kill remnant of ip_nat_dumb

This line in net/ipv4/Makefile was left behind when the rest of the
dumb NAT option was taken out.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/Makefile

@@ -11,7 +11,6 @@ obj-y     := utils.o route.o inetpeer.o protocol.o \
 
 obj-$(CONFIG_PROC_FS) += proc.o
 obj-$(CONFIG_IP_MULTIPLE_TABLES) += fib_rules.o
-obj-$(CONFIG_IP_ROUTE_NAT) += ip_nat_dumb.o
 obj-$(CONFIG_IP_MROUTE) += ipmr.o
 obj-$(CONFIG_NET_IPIP) += ipip.o
 obj-$(CONFIG_NET_IPGRE) += ip_gre.o