staging: iio: frequency: ad9834: 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.
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20220807151218.656881-3-jic23@kernel.org

drivers/staging/iio/frequency/ad9834.c

@@ -83,7 +83,7 @@ struct ad9834_state {
 	 * DMA (thus cache coherency maintenance) requires the
 	 * transfer buffers to live in their own cache lines.
 	 */
-	__be16				data ____cacheline_aligned;
+	__be16				data __aligned(IIO_DMA_MINALIGN);
 	__be16				freq_data[2];
 };