s390/ccwgroup: use BUS_NOTIFY_UNBOUND_DRIVER to trigger ungrouping

ccwgroup_notifier() currently listens for BUS_NOTIFY_UNBIND_DRIVER
events, and triggers an ungrouping for the affected device.

Looking at __device_release_driver(), we can wait for a little longer
until the driver has been fully unbound and eg. bus->remove() has been
called. So listen for BUS_NOTIFY_UNBOUND_DRIVER instead. Due to locking
the current code should work just fine, but this clarifies our intent.
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Reviewed-by: Vineeth Vijayan <vneethv@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/include/asm/ccwgroup.h

@@ -11,8 +11,7 @@ struct ccw_driver;
  * @count: number of attached slave devices
  * @dev: embedded device structure
  * @cdev: variable number of slave devices, allocated as needed
- * @ungroup_work: work to be done when a ccwgroup notifier has action
- *	type %BUS_NOTIFY_UNBIND_DRIVER
+ * @ungroup_work: used to ungroup the ccwgroup device
  */
 struct ccwgroup_device {
 	enum {

drivers/s390/cio/ccwgroup.c

@@ -401,7 +401,7 @@ static int ccwgroup_notifier(struct notifier_block *nb, unsigned long action,
 {
 	struct ccwgroup_device *gdev = to_ccwgroupdev(data);
 
-	if (action == BUS_NOTIFY_UNBIND_DRIVER) {
+	if (action == BUS_NOTIFY_UNBOUND_DRIVER) {
 		get_device(&gdev->dev);
 		schedule_work(&gdev->ungroup_work);
 	}