scsi: replace custom approach to hexdump small buffers

In kernel we have defined specifier (%*ph[C]) to dump small buffers in a
hex format. Replace custom approach by a generic one.

Cc: Jon Mason <jonmason@broadcom.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Ewan D. Milne <emilne@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>