iio: sx9310: Support ACPI property

Use device_property_read_... to support both device tree and ACPI
bindings.
Simplify the logic for reading "combined-sensors" array, as we assume
it has been vetted at firmware build time.

Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/20210728181757.187627-1-gwendal@chromium.org


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