iio: adc: qcom-spmi-adc5: Use driver datasheet_name instead of DT label

iio_chan_spec::datasheet_name expects a channel/pin name on the hardware
part, i.e. from its datasheet, instead of a friendly name from DT which
typically describes the use of said channel.  GPIO channels are commonly
specialized in QCOM board DTS based on what a - typically thermistor -
is connected to.

Also rename adc5_channel_prop::datasheet_name to channel_name to that
effect.

Signed-off-by: Marijn Suijten <marijn.suijten@somainline.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20230502-iio-adc-propagate-fw-node-label-v3-2-6be5db6e6b5a@somainline.org


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