PCI: pciehp: Drop slot workqueue

Previously the slot workqueue was used to handle events and enable or
disable the slot.  That's no longer the case as those tasks are done
synchronously in the IRQ thread.  The slot workqueue is thus merely used
to handle a button press after the 5 second delay and only one such work
item may be in flight at any given time.  A separate workqueue isn't
necessary for this simple task, so use the system workqueue instead.

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/hotplug/pciehp.h

@@ -69,7 +69,6 @@ do {									\
  *	protects scheduling, execution and cancellation of @work
  * @hotplug_lock: serializes calls to pciehp_enable_slot() and
  *	pciehp_disable_slot()
- * @wq: work queue on which @work is scheduled
  */
 struct slot {
 	u8 state;
@@ -78,7 +77,6 @@ struct slot {
 	struct delayed_work work;
 	struct mutex lock;
 	struct mutex hotplug_lock;
-	struct workqueue_struct *wq;
 };
 
 /**