scsi: docs: Update outdated link to IBM developerworks

scsi: docs: Update outdated link to IBM developerworks

IBM decided to retire a lot of the content that was previously hosted on
"developerworks", and so some of the links we've used for documentation are
now dead or redirect to some general landing page with no correlation to
what the links were meant to provide.

The s390-tools package is meanwhile also hosted on github, so we can link
to the script directly instead of to the archive.

Link: https://lore.kernel.org/r/9ab0341d6ddca46cfc885e4cd9dc38f535969b02.1593780621.git.bblock@linux.ibm.com
Reviewed-by: Julian Wiedmann <jwi@linux.ibm.com>
Reviewed-by: Steffen Maier <maier@linux.ibm.com>
Signed-off-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>