leds: rgb: ktd202x: Switch to device_for_each_child_node_scoped()

Switch to device_for_each_child_node_scoped() to simplify the code by
removing the need for calls to fwnode_handle_put() in the error path.

This also prevents possible memory leaks if new error paths are added
without the required call to fwnode_handle_put().

Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Link: https://lore.kernel.org/r/20240927-leds_device_for_each_child_node_scoped-v1-17-95c0614b38c8@gmail.com


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