iio: addac: ad74413r: fix blank line after declaration warning

Checkpatch wants a blank line after all declarations. Add it now,
even though the patch has already been submitted.

Signed-off-by: Cosmin Tanislav <cosmin.tanislav@analog.com>
Link: https://lore.kernel.org/r/20221124153049.8851-1-cosmin.tanislav@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>