title: show Cortex-M4 SWO log with openocd
body: <p>I'm using ubuntu, openocd and stlink to develop stm32f407-discovery,
  I'm learning to use ITM module through SWO pin to get log from chip. Finally, I found that openocd command</p>
  
  <pre><code>tpiu config internal /tmp/swo.out uart off 168000000
  </code></pre>
  
  <p>It's perfect to get log from the temporary file, but is there anyway to show log on openocd console directly, like semihosting log. Thanks</p>