firmware: refine firmware-factory-wipe to minimize disk access (from ToT to R12 release)

By using the new flashrom with FMAP support, we can disacrd all dd and
processing.

Execution time is reduced from 50 seconds to 23 seconds.

BUG=chromium-os:14942
TEST=time firmware-factory-wipe # 23 seconds
Cherry-picked from: http://gerrit.chromium.org/gerrit/333

Change-Id: I5fd181a79863c134bc37bb122352fbe3e165c33a
Reviewed-on: http://gerrit.chromium.org/gerrit/487
Tested-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
1 file changed