TS-7100 debian changelog

# The image date can be viewed from a booted device with:
cat /root.version

Image	Changes
ts7100-debian-stretch-20191010.tar.xz	Initial release to engineering sampling program
tsimx6-debian-buster-20200930.tar.bz2	Debian 10.6. Initial support for Rev A hardware.
tsimx6-debian-buster-20211207.tar.bz2	Debian 10.11