iio: adc: mcp3564: Use device_for_each_child_node_scoped()

Switching to the _scoped() version removes the need for manual
calling of fwnode_handle_put() in the paths where the code
exits the loop early. In this case that's all in error paths.

Reviewed-by: Marcelo Schmitt <marcelo.schmitt1@gmail.com>
Reviewed-by: Marius Cristea <marius.cristea@microchip.com>
Link: https://lore.kernel.org/r/20240428174020.1832825-2-jic23@kernel.org


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>