iio: dac: ad5504: 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: 0dbe59c7a788 ("iio:ad5504: Do not store transfer buffers on the stack")
Signed-off-by: Jonathan Cameron <[e-mail]>
Cc: Lars-Peter Clausen <[e-mail]>
Acked-by: Nuno Sá <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/iio/dac/ad5504.c

···
 	unsigned			pwr_down_mask;
 	unsigned			pwr_down_mode;
 
-	__be16				data[2] ____cacheline_aligned;
+	__be16				data[2] __aligned(IIO_DMA_MINALIGN);
 };
 
 /*