s390/dasd: fix hanging offline processing due to canceled worker

During offline processing two worker threads are canceled without
freeing the device reference which leads to a hanging offline process.
Reviewed-by: NJan Hoeppner <hoeppner@linux.ibm.com>
Signed-off-by: NStefan Haberland <sth@linux.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/block/dasd_eckd.c

@@ -2038,8 +2038,11 @@ static int dasd_eckd_basic_to_ready(struct dasd_device *device)
 
 static int dasd_eckd_online_to_ready(struct dasd_device *device)
 {
-	cancel_work_sync(&device->reload_device);
-	cancel_work_sync(&device->kick_validate);
+	if (cancel_work_sync(&device->reload_device))
+		dasd_put_device(device);
+	if (cancel_work_sync(&device->kick_validate))
+		dasd_put_device(device);
+
 	return 0;
 };