scsi: visorhba: sanitze private device data allocation

There's no need to keep the private data for a device in a separate
list; better to store it in ->hostdata and do away with the additional
list.

Signed-off-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: David Kershner <david.kershner@unisys.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>