iio: resolver: ad2s1200: 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 tag is probably not where the issue was first introduced, but
is likely to be as far as anyone considers backporting this fix.

Fixes: 0bd3d338f61b ("staging: iio: ad2s1200: Improve readability with be16_to_cpup")
Signed-off-by: Jonathan Cameron <[e-mail]>
Acked-by: Nuno Sá <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/iio/resolver/ad2s1200.c

···
 	struct spi_device *sdev;
 	struct gpio_desc *sample;
 	struct gpio_desc *rdvel;
-	__be16 rx ____cacheline_aligned;
+	__be16 rx __aligned(IIO_DMA_MINALIGN);
 };
 
 static int ad2s1200_read_raw(struct iio_dev *indio_dev,