iio: hid-sensor-humidity: Fix alignment issue of timestamp channel

This patch ensures that, there is sufficient space and correct
alignment for the timestamp.

Fixes: d7ed89d5

 ("iio: hid: Add humidity sensor support")
Signed-off-by: Ye Xiang <xiang.ye@intel.com>
Cc: <Stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20210303063615.12130-2-xiang.ye@intel.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>