sphinx: Add SPDX license headers

SPDX headers have been added to each file, and match the headers used
in the DocBook files.

(From yocto-docs rev: 79dbb0007ae24da4a3689a23e921f2a2638757f7)

Signed-off-by: Nicolas Dechesne <nicolas.dechesne@linaro.org>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/adt-manual/adt-command.rst

@@ -1,3 +1,5 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
 **********************
 Using the Command Line
 **********************

documentation/adt-manual/adt-intro.rst

@@ -1,3 +1,5 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
 *****************************************
 The Application Development Toolkit (ADT)
 *****************************************

documentation/adt-manual/adt-manual-intro.rst

@@ -1,3 +1,5 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
 ************
 Introduction
 ************

documentation/adt-manual/adt-manual.rst

@@ -1,3 +1,5 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
 ===========================================
 Yocto Project Application Developer's Guide
 ===========================================

documentation/adt-manual/adt-package.rst

@@ -1,3 +1,5 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
 ************************************************************
 Optionally Customizing the Development Packages Installation
 ************************************************************

documentation/adt-manual/adt-prepare.rst

@@ -1,3 +1,5 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
 *************************************
 Preparing for Application Development
 *************************************