[SCSI] aacraid: add 51245, 51645 and 52245 adapters to documentation.

Adding Adaptec 51245 (16 port), 51645 (20 port) and 52445 (28 port)
Universal Serial RAID controllers to the aacraid documentation.

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