scsi: zfcp: clean up unnecessary module_param_named() with no_auto_port_rescan

Improves commit 43f60cbd ("[SCSI] zfcp: No automatic port_rescan on
events")

Signed-off-by: Martin Peschke <mpeschke@linux.vnet.ibm.com>
[maier@linux.vnet.ibm.com: reword, underscore in description to match sysfs]
Signed-off-by: Steffen Maier <maier@linux.vnet.ibm.com>
Reviewed-by: Benjamin Block <bblock@linux.vnet.ibm.com>
Signed-off-by: Benjamin Block <bblock@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>