iio: magnetometer: Use aligned_s64 instead of open coding alignment.

Use this new type to both slightly simplify the code and avoid
confusing static analysis tools. Mostly this series is about consistency
to avoid this code pattern getting copied into more drivers.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://patch.msgid.link/20241215182912.481706-8-jic23@kernel.org


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