scripts/checkpatch.pl: Resync with v6.17

scripts/checkpatch.pl: Resync with v6.17

This resyncs us with the version found in v6.17 of the Linux kernel with
the following exceptions:
- Keep our u-boot specific tests / code area.
- Keep the location of our checkpatch.rst
- Change the "use strscpy" test as we don't have that to strlcpy
- Keep debug/printf in the list for $logFunctions
- Keep checks to "env" files
- Keep our tests for strncpy/strncat

This also syncs the spdxcheck.py tool and all the associated
documentation.

Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
[trini: Keep our strlcpy/cat check]
Signed-off-by: Tom Rini <trini@konsulko.com>