Add the missing 'set_status_byte()' accessor function.

Link: https://lore.kernel.org/r/20210113090500.129644-28-hare@suse.deReviewed-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>