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/ulp/srp/ib_srp.c

@@ -638,7 +638,7 @@ err:
 	if (target->state == SRP_TARGET_CONNECTING) {
 		target->state = SRP_TARGET_DEAD;
 		INIT_WORK(&target->work, srp_remove_work);
-		schedule_work(&target->work);
+		queue_work(ib_wq, &target->work);
 	}
 	spin_unlock_irq(&target->lock);
 
@@ -2199,7 +2199,7 @@ static void srp_remove_one(struct ib_device *device)
 		 * started before we marked our target ports as
 		 * removed, and any target port removal tasks.
 		 */
-		flush_scheduled_work();
+		flush_workqueue(ib_wq);
 
 		list_for_each_entry_safe(target, tmp_target,
 					 &host->target_list, list) {