PCI: al: Add Amazon Annapurna Labs PCIe host controller driver

Add driver for Amazon's Annapurna Labs PCIe host controller.  The
controller is based on DesignWare's IP.

The controller doesn't support accessing the Root Port's config space via
ECAM, so we obtain its base address via an AMZN0001 device.

Furthermore, the DesignWare PCIe controller doesn't filter out config
transactions sent to devices 1 and up on its bus, so they are filtered by
the driver.

All subordinate buses do support ECAM access.

Implementing specific PCI config access functions involves:
 - Adding an init function to obtain the Root Port's base address from
   an AMZN0001 device.
 - Adding a new entry in the MCFG quirk array.

[bhelgaas: Note that there is no Kconfig option for this driver because it
is only intended for use with the generic ACPI host bridge driver.  This
driver is only needed because the DesignWare IP doesn't completely support
ECAM access to the root bus.]

Link: https://lore.kernel.org/lkml/1553774276-24675-1-git-send-email-jonnyc@amazon.com


Co-developed-by: Vladimir Aerov <vaerov@amazon.com>
Signed-off-by: Jonathan Chocron <jonnyc@amazon.com>
Signed-off-by: Vladimir Aerov <vaerov@amazon.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>