AD5337 belongs to the same family as the AD5338.

The difference is that the AD5337 has 8-bit resolution instead of 10-bit.

Add a compatible entry for AD5337.
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20221130182632.3856675-1-festevam@gmail.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>