Constify the input to flash-write functions just like upstream

BUG=chromium:478356
BRANCH=none
TEST=still builds

Change-Id: I75b07e9ae56ca3ae3860e87929dfb312c8270a0c
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://chromium-review.googlesource.com/437326
Commit-Ready: Patrick Georgi <pgeorgi@chromium.org>
Tested-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-by: Stefan Reinauer <reinauer@chromium.org>
18 files changed