dt-bindings: timer: cdns,ttc: drop unneeded minItems

There is no need to add minItems when it is equal to maxItems.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220424150333.75172-1-krzysztof.kozlowski@linaro.org