staging: iio: resolver: ad2s1210: add label attribute support

staging: iio: resolver: ad2s1210: add label attribute support

The ad2s1210 resolver driver has quite a few channels, mostly for
internal signals for event support. This makes it difficult to know
which channel is which. This patch adds a label attribute to the
channels to make it easier to identify them.

Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://lore.kernel.org/r/20231005-ad2s1210-mainline-v4-15-ec00746840fc@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>