dt-bindings: PCI: qcom,pcie-sm8150: Document QCS615

QCS615 is derived from SM8150. Hence, add the callback with SM8150 as the
fallback.

Signed-off-by: Ziyue Zhang <quic_ziyuzhan@quicinc.com>
[mani: commit message rewording]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20250527072036.3599076-3-quic_ziyuzhan@quicinc.com

Author: ziyuezhang-123

Documentation/devicetree/bindings/pci/qcom,pcie-sm8150.yaml

@@ -16,7 +16,12 @@ description:
 
 properties:
   compatible:
-    const: qcom,pcie-sm8150
+    oneOf:
+      - const: qcom,pcie-sm8150
+      - items:
+          - enum:
+              - qcom,pcie-qcs615
+          - const: qcom,pcie-sm8150
 
   reg:
     minItems: 5