iio: ABI: document calibscale_available attributes

iio: ABI: document calibscale_available attributes

There are a number of light sensor drivers that have various
calibscale_available attributes. Up to now, these were missing from
the documentation.

Kernel version 4.8 is used since the first use appears to be in
commit eb869ade30a6 ("iio: Add tcs3472 color light sensor driver").

Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20240815-iio-abi-calib-audit-v1-1-536b2fea8620@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>