util/gitconfig: add cborg2cros.py script

util/gitconfig: add cborg2cros.py script

This is a python script that does basically the same thing as the
rebase.sh script, but in the other direction.  rebase.sh takes files
from the chromium tree (cros) and pulls them to the coreboot.org tree.
cborg2cros, as the name implies, updates patches to go into the cros
tree from coreboot.

It adds the 'UPSTREAM: ' identifier to the start of the commit message,
and uses the text '(cherry-picked from commit #####)' instead of
'Original-Commit-Id: #####'

It also adds the 'TEST=', 'BRANCH=', and 'BUG=' lines if they aren't
there.

Change-Id: Ibad9a5f0d0d2c713cf08e103c463e2e82768c436
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/15323
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>