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: 7f270bc9a2d9 ("iio: dac: AD8801: add Analog Devices AD8801/AD8803 support")
Signed-off-by: Jonathan Cameron <[e-mail]>
Acked-by: Nuno Sá <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/iio/dac/ad8801.c

···
 	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,