Replace hard tabs by spaces, and use indentation to make structure more clear

Change-Id: I8eadf9e63e04ad26e010a5a16e105446b39657c1
diff --git a/src/devices/devices_toc.cs b/src/devices/devices_toc.cs
index 9de25e1..c2ac9d5 100644
--- a/src/devices/devices_toc.cs
+++ b/src/devices/devices_toc.cs
@@ -33,18 +33,18 @@
         <ul>
           <li><a href="<?cs var:toroot ?>devices/audio_implement.html">Implementation</a></li>
           <li><a href="<?cs var:toroot ?>devices/audio_warmup.html">Warmup</a></li>
-	      <li class="nav-section">
-      		<div class="nav-section-header">
-          	<a href="<?cs var:toroot ?>devices/audio_latency.html">
-		<span class="en">Latency</span>	
-	  	</a>
-	</div>
+          <li class="nav-section">
+            <div class="nav-section-header">
+              <a href="<?cs var:toroot ?>devices/audio_latency.html">
+                <span class="en">Latency</span>
+              </a>
+            </div>
             <ul>
-		<li><a href="<?cs var:toroot ?>devices/audio_latency_measure.html">Measure</a></li>
-                <li><a href="<?cs var:toroot ?>devices/latency_design.html">Design</a></li>
-		<li><a href="<?cs var:toroot ?>devices/testing_circuit.html">Testing Circuit</a></li>
-	    </ul>
-	   </li>	
+              <li><a href="<?cs var:toroot ?>devices/audio_latency_measure.html">Measure</a></li>
+              <li><a href="<?cs var:toroot ?>devices/latency_design.html">Design</a></li>
+              <li><a href="<?cs var:toroot ?>devices/testing_circuit.html">Testing Circuit</a></li>
+            </ul>
+          </li>
           <li><a href="<?cs var:toroot ?>devices/audio_avoiding_pi.html">Priority Inversion</a></li>
           <li><a href="<?cs var:toroot ?>devices/audio_terminology.html">Terminology</a></li>
         </ul>