scsi: aic94xx: fully convert to the generic DMA API

The driver is currently using an odd mix of legacy PCI DMA API and
generic DMA API calls, switch it over to the generic API entirely.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>