[SCSI] Add VPD helper

Based on prior work by Martin Petersen and James Bottomley, this patch
adds a generic helper for retrieving VPD pages from SCSI devices.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
2 files changed