dt-bindings: PCI: cdns,cdns-pcie-host: Drop redundant msi-parent and pci-bus.yaml

The binding reference common cdns-pcie-host.yaml, which already defines
msi-parent and has a reference to pci-bus.yaml schema.  Drop redundant
pieces here to make it a bit smaller.

Link: https://lore.kernel.org/linux-pci/20240413151617.35630-1-krzysztof.kozlowski@linaro.orgSigned-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>

Documentation/devicetree/bindings/pci/cdns,cdns-pcie-host.yaml

@@ -10,7 +10,6 @@ maintainers:
   - Tom Joseph <tjoseph@cadence.com>
 
 allOf:
-  - $ref: /schemas/pci/pci-bus.yaml#
   - $ref: cdns-pcie-host.yaml#
 
 properties:
@@ -25,8 +24,6 @@ properties:
       - const: reg
       - const: cfg
 
-  msi-parent: true
-
 required:
   - reg
   - reg-names