s390: use device_remove_file_self() instead of device_schedule_callback()

driver-core now supports synchrnous self-deletion of attributes and
the asynchrnous removal mechanism is scheduled for removal.  Use it
instead of device_schedule_callback().

* Conversions in arch/s390/pci/pci_sysfs.c and
  drivers/s390/block/dcssblk.c are straightforward.

* drivers/s390/cio/ccwgroup.c is a bit more tricky because
  ccwgroup_notifier() was (ab)using device_schedule_callback() to
  purely obtain a process context to kick off ungroup operation which
  may block from a notifier callback.

  Rename ccwgroup_ungroup_callback() to ccwgroup_ungroup() and make it
  take ccwgroup_device * instead.  The new function is now called
  directly from ccwgroup_ungroup_store().

  ccwgroup_notifier() chain is updated to explicitly bounce through
  ccwgroup_device->ungroup_work.  This also removes possible failure
  from memory pressure.

Only compile-tested.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: linux390@de.ibm.com
Cc: linux-s390@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/arch/s390/include/asm/ccwgroup.h b/arch/s390/include/asm/ccwgroup.h
index 23723ce..6e670f8 100644
--- a/arch/s390/include/asm/ccwgroup.h
+++ b/arch/s390/include/asm/ccwgroup.h
@@ -23,6 +23,7 @@
 	unsigned int count;
 	struct device	dev;
 	struct ccw_device *cdev[0];
+	struct work_struct ungroup_work;
 };
 
 /**