wpan-ping: fix ifname setting

This patch fix ifname setting, we should use the ifname stored inside
this string and not give the programming declaration where to find the
string. Founded by code inspection.

Signed-off-by: Alexander Aring <aring@mojatatu.com>
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>

wpan-ping/wpan-ping.c

@@ -194,7 +194,7 @@ static int get_interface_info(struct config *conf) {
 	nl_socket_modify_cb(conf->nl_sock, NL_CB_VALID, NL_CB_CUSTOM, nl_msg_cb, conf);
 	msg = nlmsg_alloc();
 	genlmsg_put(msg, NL_AUTO_PORT, NL_AUTO_SEQ, conf->nl802154_id, 0, NLM_F_DUMP, NL802154_CMD_GET_INTERFACE, 0);
-	nla_put_string(msg, NL802154_ATTR_IFNAME, "conf->interface");
+	nla_put_string(msg, NL802154_ATTR_IFNAME, conf->interface);
 	nl_send_sync(conf->nl_sock, msg);
 
 	nl802154_cleanup(conf);