IB/sa_query: Flush scheduled work before unloading module

sa_query schedules work on IB asynchronous events.  After
unregistering the async event handler, make sure that this work has
completed before releasing the IB device (and possibly allowing the
sa_query module text to go away).

Signed-off-by: Michael S. Tsirkin <mst@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/core/sa_query.c

@@ -956,6 +956,8 @@ static void ib_sa_remove_one(struct ib_device *device)
 
 	ib_unregister_event_handler(&sa_dev->event_handler);
 
+	flush_scheduled_work();
+
 	for (i = 0; i <= sa_dev->end_port - sa_dev->start_port; ++i) {
 		ib_unregister_mad_agent(sa_dev->port[i].agent);
 		kref_put(&sa_dev->port[i].sm_ah->ref, free_sm_ah);