USB HID: avoid flush_scheduled_work()

This patch (as914) replaces a call to flush_scheduled_work() with
cancel_work_sync(), in order to help avoid potential deadlocks.
Signed-off-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

drivers/hid/usbhid/hid-core.c

@@ -956,7 +956,7 @@ static void hid_disconnect(struct usb_interface *intf)
 	usb_kill_urb(usbhid->urbctrl);
 
 	del_timer_sync(&usbhid->io_retry);
-	flush_scheduled_work();
+	cancel_work_sync(&usbhid->reset_work);
 
 	if (hid->claimed & HID_CLAIMED_INPUT)
 		hidinput_disconnect(hid);