ncr5380: Fix pseudo DMA transfers on 53C400

Pseudo-DMA (PDMA) has been broken for ages, resulting in hangs on
53C400-based cards.

According to 53C400 datasheet, PDMA transfer length must be a multiple
of 128. Check if that's true and use PIO if it's not.

This makes PDMA work on 53C400 (Canon FG2-5202).

Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>