dt-bindings: PCI: sophgo: Add dma-coherent property for SG2042

Add dma-coherent as an allowed property in the SG2042 PCIe host controller
binding. SG2042's PCIe Root Complexes are cache-coherent with the CPU.

Signed-off-by: Han Gao <gaohan@iscas.ac.cn>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20260331171248.973014-2-gaohan@iscas.ac.cn

Documentation/devicetree/bindings/pci/sophgo,sg2042-pcie-host.yaml

@@ -30,6 +30,8 @@ properties:
   device-id:
     const: 0x2042
 
+  dma-coherent: true
+
   msi-parent: true
 
 allOf:
@@ -60,5 +62,6 @@ examples:
       vendor-id = <0x1f1c>;
       device-id = <0x2042>;
       cdns,no-bar-match-nbits = <48>;
+      dma-coherent;
       msi-parent = <&msi>;
     };