faft: Add a new test to stress cgpt for switching kernel A and B

This test is intended to be run with many iterations to ensure that changing
cgpt does boot the correct kernel. One iteration of test modifies CGPT to
switch to boot kernel B and then switch back to kernel A again.

BUG=chrome-os-partner:12216
TEST=run_remote_tests.sh --remote=$REMOTE_IP -a "faft_iterations=20" \
     firmware_CgptStress/control$

Change-Id: I8922047d619f6f379606a71a3578efe950e486c3
Reviewed-on: https://gerrit.chromium.org/gerrit/30671
Reviewed-by: Vic Yang <victoryang@chromium.org>
Commit-Ready: Tom Wai-Hong Tam <waihong@chromium.org>
Tested-by: Tom Wai-Hong Tam <waihong@chromium.org>
3 files changed