cpus: hvf: unregister thread with RCU

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/cpus.c b/cpus.c
index 269d527..fe127ac 100644
--- a/cpus.c
+++ b/cpus.c
@@ -1541,6 +1541,7 @@
     cpu->created = false;
     qemu_cond_signal(&qemu_cpu_cond);
     qemu_mutex_unlock_iothread();
+    rcu_unregister_thread();
     return NULL;
 }