s390/sclp: single increment assignment control

Set a new option bit of the attach command to speed up memory
hotplug.
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/char/sclp_cmd.c

@@ -252,6 +252,7 @@ static int sclp_attach_storage(u8 id)
 	if (!sccb)
 		return -ENOMEM;
 	sccb->header.length = PAGE_SIZE;
+	sccb->header.function_code = 0x40;
 	rc = sclp_sync_request_timeout(0x00080001 | id << 8, sccb,
 				       SCLP_QUEUE_INTERVAL);
 	if (rc)