ata: ahci_mvebu: new driver for Marvell Armada 380 AHCI interfaces

The Marvell Armada 380 SoC includes two AHCI compatible
interfaces. However, like all DMA-capable Marvell interface, they
require special handling to configure MBus windows. Therefore, this
commit adds a new ahci_mvebu driver, which relies on the
libahci_platform.c code recently introduced.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Jason Cooper <jason@lakedaemon.net>
Signed-off-by: Tejun Heo <tj@kernel.org>