iio: imu: st_lsm6dsx: fix stack leak in tagged FIFO buffer

In the Linux kernel, the following vulnerability has been resolved: iio: imu: st_lsm6dsx: fix stack leak in tagged FIFO buffer The tagged FIFO path declares iio_buff on the stack with __aligned(8) but no initializer, but there is a hole in the structure, which will then leak to userspace as ST_LSM6DSX_SAMPLE_SIZE bytes (6) will be copied, but the space between that and the timestamp are not initialized. Commit c14edb4d0bdc ("iio:imu:st_lsm6dsx Fix alignment and data leak issues") moved the untagged FIFO path to a kzalloc'd buffer in hw->scan, but for the tagged path it only added the alignment qualifier and not the initializer :( Fix this by just zero-initializing the structure on the stack.