staging:iio: hid-sensors Use iio_push_to_buffer

Consistently use iio_push_to_buffer instead of manually calling the buffers
store_to callback.

These crossed with Lars-Peter's patch set doing every other case.

Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Acked-by: srinivas pandruvada <srinivas.pandruvada@intel.com>