This adds a new page to document how to use the ad7944 ADC driver.
Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://lore.kernel.org/r/20240322-mainline-ad7944-doc-v2-2-0923d35d5596@baylibre.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>