This merges flash_overwrite and flash_rw_erase to a single test binary.
BUG=chrome-os-partner:18598
TEST=Run on Spring
BRANCH=None
Change-Id: I1da7577cb5dc196178930dda3a07bb942d959866
Signed-off-by: Vic Yang <victoryang@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/48090
Reviewed-by: Randall Spangler <rspangler@chromium.org>
