iio: adc: pac1934: Use device_for_each_available_child_node_scoped() to simplify...

iio: adc: pac1934: Use device_for_each_available_child_node_scoped() to simplify error handling.

Also change both firmware parsing functions to return meaningful errors.
Whilst for the ACPI case this isn't that useful, for the generic fwnode
case we can return the errors coming from the property parsing instead
of just whether we succeeded or not.

Cc: Marius Cristea <marius.cristea@microchip.com>
Reviewed-by: Nuno Sa <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20240330190849.1321065-9-jic23@kernel.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>