mode select: Update Page Format bit behaviour

 * Page Format: Reference HP LTO 5 Vol 3_E2
 * 0 - Data is NOT SCSI-2 mode page compatible.
 *     Only parameter header and block descriptor is valid
 * 1 - Data is SCSI-2 Compatible
 *
 * IBM LTO5: Ignores PF bit but assumes SCSI-2 Compat
 * IBM 3592: Does not check this bit
 * SDLT600: If PF = 0, only parameter header and block descriptor

Signed-off-by: Mark Harvey <markh794@gmail.com>