dt-bindings: PCI: dwc: Apply common schema to Rockchip DW PCIe nodes

As the DT-bindings description states the Rockchip PCIe controller is
based on the DW PCIe RP IP-core thus its DT-nodes are supposed to be
compatible with the common DW PCIe controller schema. Let's make sure they
are evaluated against it by referring to the snps,dw-pcie.yaml schema in
the allOf sub-schemas composition.

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Serge Semin <[e-mail]>
Signed-off-by: Lorenzo Pieralisi <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>

Documentation/devicetree/bindings/pci/rockchip-dw-pcie.yaml

···
 description: |+
   RK3568 SoC PCIe host controller is based on the Synopsys DesignWare
   PCIe IP and thus inherits all the common properties defined in
-  designware-pcie.txt.
+  snps,dw-pcie.yaml.
 
 allOf:
-  - $ref: /schemas/pci/pci-bus.yaml#
+  - $ref: /schemas/pci/snps,dw-pcie.yaml#
 
 properties:
   compatible: