[SCSI] aacraid: add sysfs report of RAID level

Report the RAID level string for the SCSI device representing the
array. Report is in /sys/class/scsi_device/#:#:#:#/device/level.

Signed-off-by: Mark Salyzyn <aacraid@adaptec.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>