ref-manual: Added description for the testsdk.bbclass.

(From yocto-docs rev: 3eed6f3e244303de02cc52c16a0745b808d79e39)

Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/ref-manual/ref-classes.xml

@@ -3357,6 +3357,20 @@
     </para>
 </section>
 
+<section id='ref-classes-testsdk'>
+    <title><filename>testsdk.bbclass</filename></title>
+
+    <para>
+        This class supports running automated tests against
+        software development kits (SDKs).
+        The <filename>testsdk</filename> class runs tests on an SDK when
+        called using the following:
+        <literallayout class='monospaced'>
+     $ bitbake -c testsdk image
+        </literallayout>
+    </para>
+</section>
+
 <section id='ref-classes-texinfo'>
     <title><filename>texinfo.bbclass</filename></title>