RDMA: Update workqueue usage

* ib_wq is added, which is used as the common workqueue for infiniband
  instead of the system workqueue.  All system workqueue usages
  including flush_scheduled_work() callers are converted to use and
  flush ib_wq.

* cancel_delayed_work() + flush_scheduled_work() converted to
  cancel_delayed_work_sync().

* qib_wq is removed and ib_wq is used instead.

This is to prepare for deprecation of flush_scheduled_work().

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/ipath/ipath_driver.c

@@ -755,7 +755,7 @@ static void __devexit ipath_remove_one(struct pci_dev *pdev)
 	 */
 	ipath_shutdown_device(dd);
 
-	flush_scheduled_work();
+	flush_workqueue(ib_wq);
 
 	if (dd->verbs_dev)
 		ipath_unregister_ib_device(dd->verbs_dev);

drivers/infiniband/hw/ipath/ipath_user_pages.c

@@ -220,7 +220,7 @@ void ipath_release_user_pages_on_close(struct page **p, size_t num_pages)
 	work->mm = mm;
 	work->num_pages = num_pages;
 
-	schedule_work(&work->work);
+	queue_work(ib_wq, &work->work);
 	return;
 
 bail_mm: