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 <[e-mail]>
Signed-off-by: Thierry Reding <[e-mail]>

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

···
         compatible:
           contains:
             enum:
+              - nvidia,tegra194-host1x
+    then:
+      properties:
+        dma-coherent: true
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
               - nvidia,tegra234-host1x
     then:
       properties:
···
           description: Specification of stream IDs available for memory context device
             use. Should be a mapping of IDs 0..n to IOMMU entries corresponding to
             usable stream IDs.
+
+        dma-coherent: true
 
       required:
         - reg-names