[SCSI] hpsa: do not consider RAID level to be part of device identity

Otherwise, after doing a RAID level migration, the disk will be
disruptively removed and re-added as a different disk on rescan.

Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>