iio: adc: ad7606: rename chan_scale to a more generic chan_info

Non functional, renaming chan-related chan_scale structure to a more
generic chan_info, to host other chan specific settings, not just
scale-related.

Signed-off-by: Angelo Dureghello <adureghello@baylibre.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://patch.msgid.link/20250606-wip-bl-ad7606-calibration-v9-6-6e014a1f92a2@baylibre.com


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