net/vmnet: add vmnet backends to qapi/net

Create separate netdevs for each vmnet operating mode:
- vmnet-host
- vmnet-shared
- vmnet-bridged

Reviewed-by: Akihiko Odaki <akihiko.odaki@gmail.com>
Tested-by: Akihiko Odaki <akihiko.odaki@gmail.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Vladislav Yaroshchuk <Vladislav.Yaroshchuk@jetbrains.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>

net/vmnet-host.c

@@ -0,0 +1,24 @@
+/*
+ * vmnet-host.c
+ *
+ * Copyright(c) 2022 Vladislav Yaroshchuk <vladislav.yaroshchuk@jetbrains.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "qapi/qapi-types-net.h"
+#include "vmnet_int.h"
+#include "clients.h"
+#include "qemu/error-report.h"
+#include "qapi/error.h"
+
+#include <vmnet/vmnet.h>
+
+int net_init_vmnet_host(const Netdev *netdev, const char *name,
+                        NetClientState *peer, Error **errp) {
+  error_setg(errp, "vmnet-host is not implemented yet");
+  return -1;
+}