iio: adc: ad7266: Fix potential timestamp alignment issue.

On architectures where an s64 is only 32-bit aligned insufficient padding
would be left between the earlier elements and the timestamp. Use
aligned_s64 to enforce the correct placement and ensure the storage is
large enough.

Fixes: 54e018d ("iio:ad7266: Mark transfer buffer as __be16") # aligned_s64 is much newer.
Reported-by: David Lechner <dlechner@baylibre.com>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Reviewed-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20250413103443.2420727-2-jic23@kernel.org
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: jic23

drivers/iio/adc/ad7266.c

@@ -45,7 +45,7 @@ struct ad7266_state {
 	 */
 	struct {
 		__be16 sample[2];
-		s64 timestamp;
+		aligned_s64 timestamp;
 	} data __aligned(IIO_DMA_MINALIGN);
 };