Here are two helper functions for processing sense data.
These will allow the sd driver (and constants.c) to fetch
the information field in sense data. For a medium or
hardware error on a disk the information field is the
lba of the first failure.

Changelog:
   - add sense data helper functions:
      - scsi_sense_desc_find() to find a given
        sense descriptor (e.g. type 0 -> information)
      - scsi_get_sense_info_fld() to get the information
        field from fixed or descriptor sense data


Kai Makisara proposed the "find" function. For
example, it will help the st driver find the Filemark,
EOM and ILI flags which have been placed in the
"stream commands" sense data descriptor.

Signed-off-by: Douglas Gilbert <dougg@torque.net>