usb: don't use PREPARE_DELAYED_WORK

PREPARE_[DELAYED_]WORK() are being phased out.  They have few users
and a nasty surprise in terms of reentrancy guarantee as workqueue
considers work items to be different if they don't have the same work
function.

usb_hub->init_work is multiplexed with multiple work functions;
however, the work item is never queued while in-flight, so we can
simply use INIT_DELAYED_WORK() before each queueing.

It would probably be best to route this with other related updates
through the workqueue tree.

Lightly tested.

v2: Greg and Alan confirm that the work item is never queued while
    in-flight.  Simply use INIT_DELAYED_WORK().

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: linux-usb@vger.kernel.org

drivers/usb/core/hub.c

@@ -1040,7 +1040,7 @@ static void hub_activate(struct usb_hub *hub, enum hub_activation_type type)
 		 */
 		if (type == HUB_INIT) {
 			delay = hub_power_on(hub, false);
-			PREPARE_DELAYED_WORK(&hub->init_work, hub_init_func2);
+			INIT_DELAYED_WORK(&hub->init_work, hub_init_func2);
 			schedule_delayed_work(&hub->init_work,
 					msecs_to_jiffies(delay));
 
@@ -1194,7 +1194,7 @@ static void hub_activate(struct usb_hub *hub, enum hub_activation_type type)
 
 		/* Don't do a long sleep inside a workqueue routine */
 		if (type == HUB_INIT2) {
-			PREPARE_DELAYED_WORK(&hub->init_work, hub_init_func3);
+			INIT_DELAYED_WORK(&hub->init_work, hub_init_func3);
 			schedule_delayed_work(&hub->init_work,
 					msecs_to_jiffies(delay));
 			return;		/* Continues at init3: below */