leds: rgb: mt6370: 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 paths.

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

After switching to the scoped variant, there is no longer need for a
jump to 'fwnode_release', as an immediate return is possible. Given that
the loop is called in the probe function, and it already uses
dev_err_probe(), the common "dev_err() + return" has been updated as
well.

Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Link: https://lore.kernel.org/r/20240927-leds_device_for_each_child_node_scoped-v1-18-95c0614b38c8@gmail.com


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