scsi: core: Replace while-loop by for-loop in scsi_vpd_lun_id()

This makes the code slightly more readable.

Link: https://lore.kernel.org/r/20201029170846.14786-2-mwilck@suse.com


Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin Wilck <mwilck@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>