futility: updater: Add '--fast' for quick development

When using 'futility update' with Servo Micro or CCD, the programmer is
pretty slow that every invocation of flashrom would take a very long
time, so re-reading firmware contents when writing (flashrom -w) seems
redundant. For such usage, a '--fast' would be helpful that
 - Uses the last read image (image_current) as --diff
 - Add --noverify

TEST=make futil; tests/futility/run_test_scripts.sh $(pwd)/build/futility

Change-Id: I1ad57185160a082ea6b5c94b837a4d3ba708b587
Signed-off-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1375495
3 files changed