ahci: Add support for Cavium's fifth generation SATA controller

This patch adds support for Cavium's fifth generation SATA controller.
It is an on-chip controller and complies with AHCI 1.3.1. As the
controller uses 64-bit addresses it cannot use the standard AHCI BAR5
and so uses BAR4.

Signed-off-by: Radha Mohan Chintakuntla <rchintakuntla@cavium.com>
Signed-off-by: Tejun Heo <tj@kernel.org>