dt-bindings: display/msm/mdp4: require 4 IOMMUs

APQ8064, the only supported mdp4 platform, uses 4 IOMMUs for the MDP4
device. Update schema accordingly. When we have other MDP4 platforms,
this spec can be updated accordingly.
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/492541/
Link: https://lore.kernel.org/r/20220706145222.1565238-5-dmitry.baryshkov@linaro.orgSigned-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>

Documentation/devicetree/bindings/display/msm/mdp4.yaml

@@ -36,7 +36,7 @@ properties:
     maxItems: 1
 
   iommus:
-    maxItems: 1
+    maxItems: 4
 
   ports:
     $ref: /schemas/graph.yaml#/properties/ports