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>