dt-bindings: PCI: qcom,pcie-sa8775p: Document QCS8300

QCS8300 is derived from SA8775p. Hence, add the callback with SA8775p as
the fallback.

Signed-off-by: Ziyue Zhang <quic_ziyuzhan@quicinc.com>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20250529035635.4162149-3-quic_ziyuzhan@quicinc.com

Author: ziyuezhang-123

Documentation/devicetree/bindings/pci/qcom,pcie-sa8775p.yaml

@@ -16,7 +16,12 @@ description:
 
 properties:
   compatible:
-    const: qcom,pcie-sa8775p
+    oneOf:
+      - const: qcom,pcie-sa8775p
+      - items:
+          - enum:
+              - qcom,pcie-qcs8300
+          - const: qcom,pcie-sa8775p
 
   reg:
     minItems: 6