net: Don't warn about the default network setup

Don't warn about the default network setup that you get if no command line
-net options are specified.  There are two cases that we would otherwise
complain about:

(1) board doesn't support a NIC but the implicit "-net nic" requested one
(2) CONFIG_SLIRP not set, so the implicit "-net nic" sets up a nic that
isn't connected to anything
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

net.c

@@ -1305,6 +1305,18 @@ void net_check_clients(void)
     VLANState *vlan;
     VLANClientState *vc;
 
+    /* Don't warn about the default network setup that you get if
+     * no command line -net or -netdev options are specified. There
+     * are two cases that we would otherwise complain about:
+     * (1) board doesn't support a NIC but the implicit "-net nic"
+     * requested one
+     * (2) CONFIG_SLIRP not set, in which case the implicit "-net nic"
+     * sets up a nic that isn't connected to anything.
+     */
+    if (default_net) {
+        return;
+    }
+
     QTAILQ_FOREACH(vlan, &vlans, next) {
         int has_nic = 0, has_host_dev = 0;