vl: run "late" notifiers immediately

If a machine_init_done notifier is added late, as part of a hot-plugged
device, run it immediately.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

vl.c

@@ -2500,14 +2500,20 @@ static void qemu_run_exit_notifiers(void)
     notifier_list_notify(&exit_notifiers, NULL);
 }
 
+static bool machine_init_done;
+
 void qemu_add_machine_init_done_notifier(Notifier *notify)
 {
     notifier_list_add(&machine_init_done_notifiers, notify);
+    if (machine_init_done) {
+        notify->notify(notify, NULL);
+    }
 }
 
 static void qemu_run_machine_init_done_notifiers(void)
 {
     notifier_list_notify(&machine_init_done_notifiers, NULL);
+    machine_init_done = true;
 }
 
 static const QEMUOption *lookup_opt(int argc, char **argv,