docs: move Linux logo into a new `images` folder

Having assets in the top-level `Documentation` directory can make
it harder to find the documents one needs, especially if we want
to add more of them later on.

Instead, create a new `images` folder inside it that is used
to hold assets such as logos.

In addition, update the reference in `scripts/spdxcheck-test.sh`.

Link: https://lore.kernel.org/lkml/8735hicoy7.fsf@meer.lwn.net/
Suggested-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://lore.kernel.org/r/20220528153132.8636-1-ojeda@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

scripts/spdxcheck-test.sh: Drop python2

Since commit d0259c42abff ("spdxcheck.py: Use Python 3"), spdxcheck.py
explicitly expects to run as python3 script, there is no further point
in attempting to test with python2.

Cc: Bert Vermeulen <bert@biot.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Link: https://lore.kernel.org/r/20210707210600.7266-1-nm@ti.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

scripts: add spdxcheck.py self test

Add a script that will run spdxcheck.py through a couple of self tests to
simplify validation in the future. The tests are run for both Python 2
and Python 3 to make sure all changes to the script remain compatible
across both versions.

The script tests a regular text file (Makefile) for basic sanity checks
and then runs it on a binary file (Documentation/logo.gif) to make sure it
works in both cases. It also tests opening files passed on the command
line as well as piped files read from standard input. Finally a run on
the complete tree will be performed to catch any other potential issues.

Link: http://lkml.kernel.org/r/20181212131210.28024-2-thierry.reding@gmail.com
Signed-off-by: Thierry Reding <treding@nvidia.com>
Thomas Gleixner <tglx@linutronix.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Joe Perches <joe@perches.com>
Cc: Jeremy Cline <jcline@redhat.com>
Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>