iio: gyro: fxas210002c: 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.

Updated the comment to 'may' require.

Fixes: a0701b62 ("iio: gyro: add core driver for fxas21002c")
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Rui Miguel Silva <rui.silva@linaro.org>
Acked-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20220508175712.647246-76-jic23@kernel.org

drivers/iio/gyro/fxas21002c_core.c

@@ -150,10 +150,10 @@ struct fxas21002c_data {
 	struct regulator *vddio;
 
 	/*
-	 * DMA (thus cache coherency maintenance) requires the
-	 * transfer buffers to live in their own cache lines.
+	 * DMA (thus cache coherency maintenance) may require the
+	 * transfer buffers live in their own cache lines.
 	 */
-	s16 buffer[8] ____cacheline_aligned;
+	s16 buffer[8] __aligned(IIO_DMA_MINALIGN);
 };
 
 enum fxas21002c_channel_index {