s390/dasd: add shutdown action

Add a mechanism to wait for outstanding IO during shutdown.
Schedule the block_bh and device_bh and wait until our request queues
are empty.

Signed-off-by: Stefan Haberland <stefan.haberland@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
diff --git a/drivers/s390/block/dasd_int.h b/drivers/s390/block/dasd_int.h
index c05da00..297ac3b 100644
--- a/drivers/s390/block/dasd_int.h
+++ b/drivers/s390/block/dasd_int.h
@@ -686,6 +686,7 @@
 int dasd_generic_notify(struct ccw_device *, int);
 int dasd_generic_last_path_gone(struct dasd_device *);
 int dasd_generic_path_operational(struct dasd_device *);
+void dasd_generic_shutdown(struct ccw_device *);
 
 void dasd_generic_handle_state_change(struct dasd_device *);
 int dasd_generic_pm_freeze(struct ccw_device *);