doc: Create an intro section for testing

At present this information is hidden away. Make it more visible by
putting it first, in an intro section.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/doc/develop/index.rst b/doc/develop/index.rst
index 54e14dd..0ae4408 100644
--- a/doc/develop/index.rst
+++ b/doc/develop/index.rst
@@ -41,8 +41,8 @@
 .. toctree::
    :maxdepth: 1
 
-   coccinelle
    testing
+   coccinelle
    py_testing
    tests_writing
    tests_sandbox
diff --git a/doc/develop/testing.rst b/doc/develop/testing.rst
index ced13ac..1abe4d7 100644
--- a/doc/develop/testing.rst
+++ b/doc/develop/testing.rst
@@ -1,5 +1,7 @@
-Testing in U-Boot
-=================
+.. SPDX-License-Identifier: GPL-2.0+
+
+Introduction to testing
+=======================
 
 U-Boot has a large amount of code. This file describes how this code is
 tested and what tests you should write when adding a new feature.