iio: adc: ti-ads8688: Fix alignment of buffer in iio_push_to_buffers_with_timestamp()

iio: adc: ti-ads8688: Fix alignment of buffer in iio_push_to_buffers_with_timestamp()

[ Upstream commit 61fa5dfa5f52806f5ce37a0ba5712c271eb22f98 ]

Add __aligned(8) to ensure the buffer passed to
iio_push_to_buffers_with_timestamp() is suitable for the naturally
aligned timestamp that will be inserted.

Fixes: 74d7ec0fa77f ("iio: ti-ads8688: Update buffer allocation for timestamps")
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20210613152301.571002-5-jic23@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>