It should use ad7797_attribute_group in ad7797_info,
according to commit ("iio:ad7793: Add support for the ad7796 and ad7797").
Scale is fixed for the ad7796 and not programmable, hence
should not have the scale_available attribute.
Fixes: fd1a8b912841 ("iio:ad7793: Add support for the ad7796 and ad7797") Signed-off-by: YueHaibing <yuehaibing@huawei.com> Reviewed-by: Lars-Peter Clausen <lars@metafoo.de> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>