libata: Add another column to the ata_timing table.

The forthcoming OCTEON SOC Compact Flash driver needs an additional
timing value that was not available in the ata_timing table.  I add a
new column for dmack_hold time.  The values were obtained from the
Compact Flash specification Rev 4.1.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>