dt-bindings: drop type for operating-points-v2

The type for operating-points-v2 property is coming from dtschema
(/schemas/opp/opp.yaml), so individual bindings can just use simple
"true".

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230119131033.117324-1-krzysztof.kozlowski@linaro.org


Signed-off-by: Rob Herring <robh@kernel.org>