[SCSI] fix bugs in scsi_vpd_inquiry()

Universally, SCSI functions assume the lengths fed in are those of the buffer
to DMA data to, not the lengths of the data minus the header.
scsi_vpd_inquiry() assumed the latter and got it wrong, so fix up all the
functions to use the correct assumption (and fix a bug where INQUIRY in SCSI-2
dcannot go over 255).

[jejb: Matthew posted an identical version of this at the same time I did]
Signed-off-by: Matthew Wilcox <matthew@wil.cx>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>