staging:iio:accel:adis16201 overflow tx buffer.

Smatch caught bug.
Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/iio/accel/adis16201_ring.c

@@ -38,10 +38,12 @@ static int adis16201_read_ring_data(struct iio_dev *indio_dev, u8 *rx)
 		xfers[i].cs_change = 1;
 		xfers[i].len = 2;
 		xfers[i].delay_usecs = 20;
-		xfers[i].tx_buf = st->tx + 2 * i;
-		st->tx[2 * i] = ADIS16201_READ_REG(ADIS16201_SUPPLY_OUT +
-						   2 * i);
-		st->tx[2 * i + 1] = 0;
+		if (i < ADIS16201_OUTPUTS) {
+			xfers[i].tx_buf = st->tx + 2 * i;
+			st->tx[2 * i] = ADIS16201_READ_REG(ADIS16201_SUPPLY_OUT +
+							   2 * i);
+			st->tx[2 * i + 1] = 0;
+		}
 		if (i >= 1)
 			xfers[i].rx_buf = rx + 2 * (i - 1);
 		spi_message_add_tail(&xfers[i], &msg);