stex: Support to Pegasus series.

Pegasus is a high performace hardware RAID solution designed to unleash
the raw power of Thunderbolt technology.

1. Add code to distinct SuperTrack and Pegasus series by sub device ID.
   It should support backward compatibility.

2. Change the driver version.

Signed-off-by: Charles Chiou <charles.chiou@tw.promise.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>