libata-pmp: add support for Thermaltake BlackX Duet esata drive dock

Some errors still show up, but the dock works, both drives can be
accessed at the same time

The chip maker and designation is unknown - possibly jmicron JMB350?

Signed-off-by: Pavel Herrmann <morpheus.ibis@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>