iio: resolver: ad2s1200: Fix alignment for DMA safety

____cacheline_aligned is an insufficient guarantee for non-coherent DMA
on platforms with 128 byte cachelines above L1.  Switch to the updated
IIO_DMA_MINALIGN definition.

Fixes tag is probably not where the issue was first introduced, but
is likely to be as far as anyone considers backporting this fix.

Fixes: 0bd3d338 ("staging: iio: ad2s1200: Improve readability with be16_to_cpup")
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20220508175712.647246-89-jic23@kernel.org