dt-bindings: PCI: designware: Add binding for CDM register check

Add support to enable CDM (Configuration Dependent Module) registers check
for any data corruption. CDM registers include standard PCIe configuration
space registers, Port Logic registers and iATU and DMA registers.
Refer Section S.4 of Synopsys DesignWare Cores PCI Express Controller Databook
Version 4.90a.
Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/pci/designware-pcie.txt

@@ -34,6 +34,11 @@ Optional properties:
 - clock-names: Must include the following entries:
 	- "pcie"
 	- "pcie_bus"
+- snps,enable-cdm-check: This is a boolean property and if present enables
+   automatic checking of CDM (Configuration Dependent Module) registers
+   for data corruption. CDM registers include standard PCIe configuration
+   space registers, Port Logic registers, DMA and iATU (internal Address
+   Translation Unit) registers.
 RC mode:
 - num-viewport: number of view ports configured in hardware. If a platform
   does not specify it, the driver assumes 2.