usb: usbtmc: Fix disconnect/poll interaction

When the device is disconnected poll waiters were not being woken.

Changes for v2:
  - add commit summary
  - add Fixes and Reported-by tags

Fixes: eb6b92ecc0f9 ("Add support for receiving USBTMC USB488 SRQ notifications via poll/select")
Reported-by: Oliver Neukum <oneukum@suse.com>
Signed-off-by: Dave Penkler <dpenkler@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/class/usbtmc.c

@@ -1525,13 +1525,14 @@ static void usbtmc_disconnect(struct usb_interface *intf)
 	dev_dbg(&intf->dev, "usbtmc_disconnect called\n");
 
 	data = usb_get_intfdata(intf);
-	usbtmc_free_int(data);
 	usb_deregister_dev(intf, &usbtmc_class);
 	sysfs_remove_group(&intf->dev.kobj, &capability_attr_grp);
 	sysfs_remove_group(&intf->dev.kobj, &data_attr_grp);
 	mutex_lock(&data->io_mutex);
 	data->zombie = 1;
+	wake_up_all(&data->waitq);
 	mutex_unlock(&data->io_mutex);
+	usbtmc_free_int(data);
 	kref_put(&data->kref, usbtmc_delete);
 }