leds: is31fl319x: Use device_for_each_child_node_scoped() to access child nodes

The iterated nodes are direct children of the device node, and the
`device_for_each_child_node()` macro accounts for child node
availability.

`fwnode_for_each_available_child_node()` is meant to access the child
nodes of an fwnode, and therefore not direct child nodes of the device
node.

In this case, the child nodes are not required outside the loop, and
the scoped version of the macro can be used to remove the repetitive
`goto put` pattern.

Use `device_for_each_child_node_scoped_scoped()` to indicate device's
direct child nodes.

Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20240721-device_for_each_child_node-available-v2-4-f33748fd8b2d@gmail.com


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