iio: adc: hi8435: 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: 72aa29ce ("iio: adc: hi8435: Holt HI-8435 threshold detector")
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20220508175712.647246-21-jic23@kernel.org

drivers/iio/adc/hi8435.c

@@ -49,7 +49,7 @@ struct hi8435_priv {
 
 	unsigned threshold_lo[2]; /* GND-Open and Supply-Open thresholds */
 	unsigned threshold_hi[2]; /* GND-Open and Supply-Open thresholds */
-	u8 reg_buffer[3] ____cacheline_aligned;
+	u8 reg_buffer[3] __aligned(IIO_DMA_MINALIGN);
 };
 
 static int hi8435_readb(struct hi8435_priv *priv, u8 reg, u8 *val)