iio: potentiometer: max5481: 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: df1fd2de ("iio: max5481: Add support for Maxim digital potentiometers")
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20220508175712.647246-83-jic23@kernel.org

drivers/iio/potentiometer/max5481.c

@@ -44,7 +44,7 @@ static const struct max5481_cfg max5481_cfg[] = {
 struct max5481_data {
 	struct spi_device *spi;
 	const struct max5481_cfg *cfg;
-	u8 msg[3] ____cacheline_aligned;
+	u8 msg[3] __aligned(IIO_DMA_MINALIGN);
 };
 
 #define MAX5481_CHANNEL {					\