dt-bindings: PCI: dwc: Add AMD Versal2 MDB SLCR support

Add support for MDB System Level Control and Status Register (SLCR)
aperture that is only supported for AMD Versal2 devices.

Signed-off-by: Thippeswamy Havalige <thippeswamy.havalige@amd.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Acked-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20250228093351.923615-2-thippeswamy.havalige@amd.com
[kwilczynski: commit log]
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>

Author: Thippeswamy Havalige

Documentation/devicetree/bindings/pci/snps,dw-pcie.yaml

@@ -113,6 +113,8 @@ properties:
               enum: [ smu, mpu ]
             - description: Tegra234 aperture
               enum: [ ecam ]
+            - description: AMD MDB PCIe SLCR region
+              const: slcr
     allOf:
       - contains:
           const: dbi