iio: chemical: sps30: use aligned_s64 for timestamp

Follow the pattern of other drivers and use aligned_s64 for the
timestamp. This will ensure that the timestamp is correctly aligned on
all architectures.

Fixes: a5bf6fdd ("iio:chemical:sps30: Fix timestamp alignment")
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-v1-5-eafac1e22318@baylibre.com


Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>