updater: Allow specifying MP FWID / ECID.

We need to specify MP versions in ebuild file and then send to updater for
checking RO/RW updating rules.

BUG=chromium:299711
TEST=emerge-link chromeos-firmware-link.

Change-Id: Ie5b0f3c033dfb9a7d77c9c431f0a60b5d51ae832
Reviewed-on: https://chromium-review.googlesource.com/170893
Tested-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Commit-Queue: Hung-Te Lin <hungte@chromium.org>