iio: temp: maxim_thermocouple: 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: 1f25ca1 ("iio: temperature: add support for Maxim thermocouple chips")
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Matt Ranostay <mranostay@gmail.com>
Acked-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20220508175712.647246-93-jic23@kernel.org

drivers/iio/temperature/maxim_thermocouple.c

@@ -122,7 +122,7 @@ struct maxim_thermocouple_data {
 	struct spi_device *spi;
 	const struct maxim_thermocouple_chip *chip;
 
-	u8 buffer[16] ____cacheline_aligned;
+	u8 buffer[16] __aligned(IIO_DMA_MINALIGN);
 	char tc_type;
 };