iio: dac: ad8801: 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: 7f270bc9a2 ("iio: dac: AD8801: add Analog Devices AD8801/AD8803 support")
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20220508175712.647246-59-jic23@kernel.org

drivers/iio/dac/ad8801.c

@@ -26,7 +26,7 @@ struct ad8801_state {
 	struct regulator *vrefh_reg;
 	struct regulator *vrefl_reg;
 
-	__be16 data ____cacheline_aligned;
+	__be16 data __aligned(IIO_DMA_MINALIGN);
 };
 
 static int ad8801_spi_write(struct ad8801_state *state,