iio: hid-sensor-prox: Fix invalid read_raw for attention

The attention channel is a IIO_CHAN_INFO_PROCESSED, not a
IIO_CHAN_INFO_RAW.

Modify prox_read_raw() to support it.

Fixes: 596ef5cf ("iio: hid-sensor-prox: Add support for more channels")
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Link: https://patch.msgid.link/20241122-fix-processed-v2-1-b9f606d3b519@chromium.org


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