PCI: aardvark: Add Aardvark PCI host controller driver

Add a driver for the Aardvark PCIe controller used on the Marvell Armada
3700 ARM64 SoC.

Based on work done by Hezi Shahmoon <hezi.shahmoon@marvell.com> and Marcin
Wojtas <mw@semihalf.com>.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>