dt-bindings: dp-connector: Drop maxItems from -supply

The meta-schema recently gained a definition for the common -supply$
property, which denotes that maxItems is not a valid property. Drop this
to clear up the binding validation error.

Fixes: a46c112512 ("dt-bindings: dp-connector: add binding for DisplayPort connector")
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Rob Herring <robh@kernel.org>
(cherry picked from commit ca230ab187)
Link: https://patchwork.freedesktop.org/patch/msgid/20210120175922.1579835-1-bjorn.andersson@linaro.org

Documentation/devicetree/bindings/display/connector/dp-connector.yaml

@@ -26,7 +26,6 @@ properties:
 
   dp-pwr-supply:
     description: Power supply for the DP_PWR pin
-    maxItems: 1
 
   port:
     $ref: /schemas/graph.yaml#/properties/port