ahci: disable PMP for marvell ahcis

Marvell ahcis don't play nicely with PMPs.  Disable it.

Reported by KueiHuan Chen in the following thread.

  http://thread.gmane.org/gmane.linux.ide/33296



Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: KueiHuan Chen <kueihuan.chen@gmail.com>
Cc: Mark Lord <mlord@pobox.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>