checkpatch: import new script version from kernel v6.0-rc3

checkpatch: import new script version from kernel v6.0-rc3

Replace existing checkpatch script with the one available in the
latest Linux kernel.
Add also from the same kernel version the spelling database and
the script spdxcheck.py, even if the script cannot be found by
checkpatch in the current path.
Add an empty "const_structs.checkpatch" file and an initial
"spdxexclude" file.

The script as is doesn't work properly in OpenOCD project.
Further patches in this series are required.

Gerrit will use the checkpatch in this commit to test/build the
commit itself. A minimal configuration file is then required to
avoid a failure in the test/build process.

This commit includes the OpenOCD commits:
commit 164450a01576 ("Change checkpatch.pl tab expanding to 4 characters.")
commit 667d510dabd5 ("checkpatch: fix false indent trigger")
already merged in upstream checkpatch in kernel v6.0-rc3.

Change-Id: Ic9cdecff2df0a1e23cdb01d10f14c5988480b8d6
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/5116
Tested-by: jenkins