scsi: hpsa: add 'ctlr_num' sysfs attribute

Add a sysfs attribute 'ctlr_num' holding the current HPSA controller
number. This is required to construct compability 'cciss' links.

[mkp: fixed typo]

Signed-off-by: Hannes Reinecke <hare@suse.com>
Acked-by: Don Brace <don.brace@microsemi.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>