lint: convert checkpatch_json.py to python 3
Align all coreboot scripts on one python version.
Tested by running the original suggested test:
$ nice -n 20 git diff HEAD~ | util/lint/checkpatch.pl \
--no-signoff -q - | tee checkpatch.txt
$ util/lint/checkpatch_json.py checkpatch.txt \
comment.json checkpatch.txt
Change-Id: Iec2bb0be23b27a3eaf92f293c962a8e6bfb03af0
Signed-off-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/42318
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Singer <felixsinger@posteo.net>
