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: NHannes Reinecke <hare@suse.com>
Acked-by: NDon Brace <don.brace@microsemi.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>