hpsa: do not use a void pointer for scsi_cmd field of struct CommandList

There's no reason for it to be a void *, it should be a struct scsi_cmnd *

Reviewed-by: Scott Teel <scott.teel@pmcs.com>
Signed-off-by: Don Brace <don.brace@pmcs.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>