scsi: Rework the code for caching Vital Product Data (VPD)

scsi: Rework the code for caching Vital Product Data (VPD)

Introduce the scsi_get_vpd_buf() and scsi_update_vpd_page()
functions. The only functional change in this patch is that if updating
page 0x80 fails that it is attempted to update page 0x83.

Signed-off-by: Bart Van Assche <[email protected]>
Acked-by: Hannes Reinecke <[email protected]>
Reviewed-by: Shane Seymour <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Johannes Thumshirn <[email protected]>
Cc: Shane M Seymour <[email protected]>
Signed-off-by: Martin K. Petersen <[email protected]>