iio:ad7476: Use iio_push_to_buffers_with_timestamp()

	struct iio_poll_func *pf = p;

	struct iio_dev *indio_dev = pf->indio_dev;

	struct ad7476_state *st = iio_priv(indio_dev);

	s64 time_ns;

	int b_sent;

	b_sent = spi_sync(st->spi, &st->msg);

	if (b_sent < 0)

		goto done;

	time_ns = iio_get_time_ns();

	if (indio_dev->scan_timestamp)

		((s64 *)st->data)[1] = time_ns;

	iio_push_to_buffers(indio_dev, st->data);

	iio_push_to_buffers_with_timestamp(indio_dev, st->data,

		iio_get_time_ns());

done:

	iio_trigger_notify_done(indio_dev->trig);