net: return correct error code

When kmemdup called failed and register_net_sysctl return NULL, should
return ENOMEM instead of ENOBUFS
Signed-off-by: Nliuguoqiang <liuguoqiang@uniontech.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/devinet.c

@@ -2591,7 +2591,7 @@ static int __devinet_sysctl_register(struct net *net, char *dev_name,
 free:
 	kfree(t);
 out:
-	return -ENOBUFS;
+	return -ENOMEM;
 }
 
 static void __devinet_sysctl_unregister(struct net *net,