dt-bindings: display: tegra: Allow dma-coherent on Tegra194 and later

Tegra194 and later chips have a coherency fabric, so some devices can be
marked as DMA coherent to avoid unnecessary cache maintenance.

Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>

Documentation/devicetree/bindings/display/tegra/nvidia,tegra20-host1x.yaml

@@ -177,6 +177,15 @@ allOf:
 
       required:
         - reg-names
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - nvidia,tegra194-host1x
+    then:
+      properties:
+        dma-coherent: true
   - if:
       properties:
         compatible:
@@ -226,6 +235,8 @@ allOf:
             use. Should be a mapping of IDs 0..n to IOMMU entries corresponding to
             usable stream IDs.
 
+        dma-coherent: true
+
       required:
         - reg-names