dt-bindings: display: msm/dp: restrict opp-table to objects

Simple 'opp-table:true' accepts a boolean property as opp-table, so
restrict it to object to properly enforce real OPP table nodes.
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230820080543.25204-1-krzysztof.kozlowski@linaro.orgSigned-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/display/msm/dp-controller.yaml

@@ -79,7 +79,8 @@ properties:
 
   operating-points-v2: true
 
-  opp-table: true
+  opp-table:
+    type: object
 
   power-domains:
     maxItems: 1