leds: max5970: Fix unreleased fwnode_handle in probe function

leds: max5970: Fix unreleased fwnode_handle in probe function

An object initialized via device_get_named_child_node() requires calls
to fwnode_handle_put() when it is no longer required to avoid leaking
memory.

Add the automatic cleanup facility for 'led_node' to ensure that
fwnode_handle_put() is called in all execution paths.

Fixes: 736214b4b02a ("leds: max5970: Add support for max5970")
Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Link: https://lore.kernel.org/r/20241031-max5970-of_node_put-v2-1-0ffe1f1d3bc9@gmail.com
Signed-off-by: Lee Jones <lee@kernel.org>