qdev: add HotplugHandler->post_plug() callback

The ->pre_plug() callback is invoked before the device is realized.  The
->plug() callback is invoked when the device is being realized but
before it is reset.

This patch adds a ->post_plug() callback which is invoked after the
device has been reset.  This callback is needed by HotplugHandlers that
need to wait until after ->reset().

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20180716083732.3347-2-stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index cf0db4b..529b82d 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -867,6 +867,10 @@
             device_reset(dev);
         }
         dev->pending_deleted_event = false;
+
+        if (hotplug_ctrl) {
+            hotplug_handler_post_plug(hotplug_ctrl, dev);
+        }
     } else if (!value && dev->realized) {
         Error **local_errp = NULL;
         QLIST_FOREACH(bus, &dev->child_bus, sibling) {