Add migration instructions gathered by combing the commits in this
release.
(From yocto-docs rev: b864f8570271df4e6cb47d21cb658d13ffd1d8f5)
Signed-off-by: Paul Eggleton <paul.eggleton@microsoft.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>