[libata] SCSI VPD page 0x83 fixes

Original patch (and description) by Douglas Gilbert, with minor fixes
and API updates from me.

Changelog:
  - make existing libata VPD device identification page (0x83)
    supply the ATA serial number in the libata "vendor
    specific" designator (from Chris Paulson-Ellis)
  - add a "t10 vendor id based" designator as defined in
    SAT rev 08 (section 10.3.4.2.3) that supplies ATA
    model and serial numbers
  - make the libata VPD page 0x83 more extensible (for
    adding more designators in the future).
  - rename EVPD to VPD in various places. Enable Vital
    Product Data (EVPD) is a bit in the INQUIRY cdb.

Signed-off-by: Jeff Garzik <jeff@garzik.org>