cpuidle: dt_idle_genpd: Simplify with scoped for each OF child loop

Use scoped for_each_child_of_node_scoped() when iterating over device
nodes to make code a bit simpler.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20240816150931.142208-4-krzysztof.kozlowski@linaro.org


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>