thermal: qcom: qcom-spmi-adc-tm5: convert to IIO fwnode API

Make usage of the new firmware agnostic API
'devm_of_iio_channel_get_by_name()' to get the IIO channel.

Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20220715122903.332535-7-nuno.sa@analog.com


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