net/slirp: Deprecate the [hub_id name] parameter tuple

The "name" in the [hub_id name] parameter tuple is the same as a
"netdev_id" (which should be unique), so specifying the hub_id here
is just redundant (it was likely just necessary in the past when
the network subsystem was still using "vlans" only and when it did
not use unique "id"s yet).

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

net/slirp.c

@@ -404,6 +404,8 @@ static SlirpState *slirp_lookup(Monitor *mon, const char *hub_id,
                 monitor_printf(mon, "unrecognized (hub-id, stackname) pair\n");
                 return NULL;
             }
+            warn_report("Using 'hub-id' is deprecated, specify the netdev id "
+                        "directly instead");
         } else {
             nc = qemu_find_netdev(name);
             if (!nc) {