rxrpc: Fix dependency on IPv6 in udp tunnel config

As udp_port_cfg struct changes its members with dependency on IPv6
configuration, the code in rxrpc should also check for IPv6.

Fixes: 1a9b86c9fd95 ("rxrpc: use udp tunnel APIs instead of open code in rxrpc_open_socket")
Reported-by: kernel test robot <[e-mail]>
Signed-off-by: Vadim Fedorenko <[e-mail]>
Acked-by: David Howells <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/rxrpc/local_object.c

···
 	if (udp_conf.family == AF_INET) {
 		udp_conf.local_ip = srx->transport.sin.sin_addr;
 		udp_conf.local_udp_port = srx->transport.sin.sin_port;
+#if IS_ENABLED(CONFIG_AF_RXRPC_IPV6)
 	} else {
 		udp_conf.local_ip6 = srx->transport.sin6.sin6_addr;
 		udp_conf.local_udp_port = srx->transport.sin6.sin6_port;
+#endif
 	}
 	ret = udp_sock_create(net, &udp_conf, &local->socket);
 	if (ret < 0) {