iio_push_to_buffers_with_timestamp assumes 8 byte alignment which
is not guaranteed by an array of smaller elements.

Note that whilst in this particular case the alignment forcing
of the ts element is not strictly necessary it acts as good
documentation.  Doing this where not necessary should cut
down on the number of cut and paste introduced errors elsewhere.

Fixes: 0427a106 ("iio: accel: kxsd9: Add triggered buffer handling")
Reported-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: <Stable@vger.kernel.org>