iio: adc: vf610: Simplify with dev_err_probe

Use dev_err_probe() to make error code handling simpler and handle
deferred probe nicely (avoid spamming logs).

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://patch.msgid.link/20250713-iio-clk-get-enabled-v1-3-70abc1f9ce6c@linaro.org


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