staging:iio:gyro:adis16130 fix adis16130_spi_read which was never selecting the channel

	int ret;

	struct iio_dev *indio_dev = dev_get_drvdata(dev);

	struct adis16130_state *st = iio_priv(indio_dev);

	struct spi_message msg;

	struct spi_transfer xfer = {

		.tx_buf = st->buf,

		.rx_buf = st->buf,

	};

	mutex_lock(&st->buf_lock);

	st->buf[0] = ADIS16130_CON_RD | reg_addr;

	st->buf[1] = st->buf[2] = st->buf[3] = 0;

	if (st->mode)

		ret = spi_read(st->us, st->buf, 4);

		xfer.len = 4;

	else

		ret = spi_read(st->us, st->buf, 3);

		xfer.len = 3;

	spi_message_init(&msg);

	spi_message_add_tail(&xfer, &msg);

	ret = spi_sync(st->us, &msg);

	if (ret == 0) {

		if (st->mode)

			*val = (st->buf[1] << 16) |