iio: adc: qcom-pm8xxx-xoadc: drop unused kerneldoc struct pm8xxx_chan_info member

iio: adc: qcom-pm8xxx-xoadc: drop unused kerneldoc struct pm8xxx_chan_info member

Drop description of non-existing 'struct pm8xxx_chan_info' member:

  qcom-pm8xxx-xoadc.c:386: warning: Excess struct member 'scale_fn_type' description in 'pm8xxx_chan_info'

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20240225202744.60500-1-krzysztof.kozlowski@linaro.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>