cpuidle: riscv-sbi: 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.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://patch.msgid.link/20240820094023.61155-2-krzysztof.kozlowski@linaro.org


Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>