The PCIe spec (r3.0, sec 7.2.2) specifies an "Enhanced Configuration Access
Mechanism" (ECAM) for memory-mapped access to configuration space.  ECAM is
required for PCIe systems unless there's a standard firmware interface for
config access.

In the absence of a firmware interface, we use pci_generic_ecam_ops, and on
ACPI systems, we discover the ECAM space via the MCFG table and/or the _CBA
method.

Unfortunately some systems provide MCFG but don't implement ECAM according
to spec, so we need a mechanism for quirks to make those systems work.

Add an MCFG quirk mechanism to override the config accessor functions
and/or the memory-mapped address space.

A quirk is selected if it matches all of the following:

  - OEM ID
  - OEM Table ID
  - OEM Revision
  - PCI segment (from _SEG)
  - PCI bus number range (from _CRS, wildcard allowed)

If the quirk specifies config accessor functions or a memory-mapped address
range, these override the defaults.

[bhelgaas: changelog, reorder quirk matching, fix oem_revision typo per
Duc, add under #ifdef CONFIG_PCI_QUIRKS]
Signed-off-by: Tomasz Nowicki <tn@semihalf.com>
Signed-off-by: Dongdong Liu <liudongdong3@huawei.com>
Signed-off-by: Christopher Covington <cov@codeaurora.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>