scsi: myrb: Add Mylex RAID controller (block interface)

This patch adds support for the Mylex DAC960 RAID controller,
supporting the older, block-based interface only.  The driver is a
re-implementation of the original DAC960 driver.

Signed-off-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>