dt-bindings: display: sprd,sharkl3-dpu: Fix missing clocks constraints

'minItems' alone does not impose upper bound, unlike 'maxItems' which
implies lower bound.  Add missing clock constraint so the list will have
exact number of items (clocks).

Fixes: 8cae15c6 ("dt-bindings: display: add Unisoc's dpu bindings")
Cc: stable@vger.kernel.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20250720123003.37662-3-krzysztof.kozlowski@linaro.org


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