libcamera: Add missing SPDX headers

Multiple files in libcamera are missing SPDX headers. Add them with the
following licenses:

- CC-BY-SA-4.0 for documentation

- CC0-1.0 for build system, development tool configuration files and
  TODO lists, as we consider them non-copyrightable, and for example
  configuration files to facilitate their use

- BSD-2-Clause for a file copied from the Raspberry Pi tuning tool (and
  add the corresponding copyright information)

While at it, add a missing blank line to
src/libcamera/pipeline/virtual/README.md.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com>

src/libcamera/pipeline/virtual/README.md

@@ -1,3 +1,5 @@
+<!-- SPDX-License-Identifier: CC-BY-SA-4.0 -->
+
 # Virtual Pipeline Handler
 
 Virtual pipeline handler emulates fake external camera(s) for testing.
@@ -9,6 +11,7 @@ Virtual pipeline handler emulates fake external camera(s) for testing.
   `share/libcamera/pipeline/virtual/virtual.yaml`.
 
 ### Config File Format
+
 The config file contains the information about cameras' properties to register.
 The config file should be a yaml file with dictionary of the cameraIds
 associated with their properties as top level. The default value will be applied

src/libcamera/pipeline/virtual/data/meson.build

@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: CC0-1.0
+
 install_data('virtual.yaml',
              install_dir : pipeline_data_dir / 'virtual',
              install_tag : 'runtime',

src/libcamera/software_isp/TODO.md

@@ -1,3 +1,5 @@
+<!-- SPDX-License-Identifier: CC0-1.0 -->
+
 # Software ISP TODO list
 
 This file contains the TODO list for the software ISP.