iio: adc: ad4130: Use automatic cleanup of locks and direct mode.

Reduces boilerplate and allows for simpler to follow direct returns.

Reviewed-by: Nuno Sa <nuno.a@analog.com>
Link: https://lore.kernel.org/r/20240128150537.44592-10-jic23@kernel.org


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