backlight: 88pm860x_bl: 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: Jinjie Ruan <ruanjinjie@huawei.com>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20240822062546.3490076-1-ruanjinjie@huawei.com


Signed-off-by: Lee Jones <lee@kernel.org>