scsi: docs: Remove invalid link and update text for zfcp kernel config

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.

Change the provided link in the Kconfig file for zfcp to rather refer to
our device drivers book that we regularly update and publish for free, and
whose name hasn't been changed since it was first published.

Our hardware is also not called "IBM eServer zSeries" anymore - in fact, it
hasn't been called like that since 2006. Use a broader term that covers
different server names over time.

Lastly, add a short paragraph about how our HBAs are typically named, to
have some more tangible references.

Link: https://lore.kernel.org/r/96069b9f4c4f056a515b37e89b2bdfccc282e3d3.1593780621.git.bblock@linux.ibm.comReviewed-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>

drivers/scsi/Kconfig

@@ -1469,14 +1469,19 @@ config SCSI_SUNESP
 	  module will be called sun_esp.
 
 config ZFCP
-	tristate "FCP host bus adapter driver for IBM eServer zSeries"
+	tristate "FCP host bus adapter driver for IBM mainframes"
 	depends on S390 && QDIO && SCSI
 	depends on SCSI_FC_ATTRS
 	help
-          If you want to access SCSI devices attached to your IBM eServer
-          zSeries by means of Fibre Channel interfaces say Y.
-          For details please refer to the documentation provided by IBM at
-          <http://oss.software.ibm.com/developerworks/opensource/linux390>
+	  If you want to access SCSI devices attached to your IBM mainframe by
+	  means of Fibre Channel Protocol host bus adapters say Y.
+
+	  Supported HBAs include different models of the FICON Express and FCP
+	  Express I/O cards.
+
+	  For a more complete list, and for more details about setup and
+	  operation refer to the IBM publication "Device Drivers, Features, and
+	  Commands", SC33-8411.
 
           This driver is also available as a module. This module will be
           called zfcp. If you want to compile it as a module, say M here