iio: addac: ad74413r: use aligned_s64 for timestamp

Follow the pattern of other drivers and use aligned_s64 for the
timestamp. Technically there was no issue here since
AD74413R_FRAME_SIZE * AD74413R_CHANNEL_MAX == 16 and IIO_DMA_MINALIGN
is always a multiple of 8. But best to conform in case someone copies
this to new code and then tweaks something.

Also move the unaligned.h header while touching this since it was the
only one not in alphabetical order.

Signed-off-by: David Lechner <dlechner@baylibre.com>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Link: https://patch.msgid.link/20250417-iio-more-timestamp-alignment-v1-3-eafac1e22318@baylibre.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>