dt-bindings: usb: snps,dwc3: Add missing 'dma-coherent' property

The 'unevaluatedProperties' schema checks is not fully working and doesn't catch some cases where there's a $ref to another schema. A fix is pending, but results in new warnings in examples.

Some DWC3 implementations such as Xilinx are hooked up coherently and need to set the 'dma-coherent' property.

---
 Documentation/devicetree/bindings/usb/snps,dwc3.yaml | 2 ++
 1 file changed, 2 insertions(+)

index f4471f8bdbef..d41265ba8ce2 100644
@@ -68,6 +68,8 @@ properties:
         - enum: [bus_early, ref, suspend]
         - true
 
+  dma-coherent: true
+
   iommus:
     maxItems: 1
 

2.34.1

Applied, thanks.