iio: adc: rockchip: correct alignment of timestamp

iio: adc: rockchip: correct alignment of timestamp

I assume this device is only used on architectures where a 8 byte
integer type is always 8 byte aligned.  However, I would prefer IIO
drivers to never make that assumption as the code gets copied into
new drivers which are not so tightly couple to one driver and those
can run on architectures that align these types to only 4 bytes in which
case this structure may be 4 byte to small leading to a buffer overrun.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://patch.msgid.link/20241215182912.481706-21-jic23@kernel.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>