iio: adc: ad7768-1: Fix insufficient alignment of timestamp.

iio: adc: ad7768-1: Fix insufficient alignment of timestamp.

On architectures where an s64 is not 64-bit aligned, this may result
insufficient alignment of the timestamp and the structure being too small.
Use aligned_s64 to force the alignment.

Fixes: a1caeebab07e ("iio: adc: ad7768-1: Fix too small buffer passed to iio_push_to_buffers_with_timestamp()") # aligned_s64 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/20250413103443.2420727-3-jic23@kernel.org
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>