net: Provide VLAN client lookup helper

Introduce qemu_find_vlan_client_by_name for VLANClientState lookup based
on VLAN ID and client name. This is useful for monitor commands.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/net.h b/net.h
index 6702f42..a5ae730 100644
--- a/net.h
+++ b/net.h
@@ -51,7 +51,7 @@
     int delivering;
 };
 
-VLANState *qemu_find_vlan(int id);
+VLANState *qemu_find_vlan(int id, int allocate);
 VLANClientState *qemu_new_vlan_client(VLANState *vlan,
                                       const char *model,
                                       const char *name,