iio: adc: ad7380: rename internal_ref_only

Rename adaq_internal_ref_only to internal_ref_only_adaq. There are non-
ADAQ chips in the family that are also internal reference only, so the
adaq_ prefix is misleading.

Signed-off-by: David Lechner <dlechner@baylibre.com>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Link: https://patch.msgid.link/20250401-iio-ad7380-add-ad7389-4-v1-2-23d2568aa24f@baylibre.com


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