Add I/O register mapping for NCR53C400A and enable PDMA mode to
improve performance and fix non-working IRQ.

Tested with HP C2502 (and user-space enabler).
Signed-off-by: NOndrej Zary <linux@rainbow-software.org>
Signed-off-by: NFinn Thain <fthain@telegraphics.com.au>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>