PCI: altera: Add Altera PCIe host controller driver

Add the Altera PCIe host controller driver.

[bhelgaas: whitespace, fold in DT and maintainer updates, OF_PCI
dependency from Arnd]
Signed-off-by: Ley Foon Tan <lftan@altera.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Acked-by: Rob Herring <robh@kernel.org> (DT binding)