Implement no-op commands

Provide implementations for "boot" and "legacy" that error out in MTD mode and
"repair" that is a no-op. Eventually if/when we add redundancy, repair will do
something, but boot/legacy never will.

BUG=chromium:221745
BRANCH=none
TEST=none

Original-Change-Id: Ie537f20d8dff9d14fb83d0431bd48453bff0217d
Reviewed-on: https://gerrit.chromium.org/gerrit/46883
Commit-Queue: Albert Chaulk <achaulk@chromium.org>
Reviewed-by: Albert Chaulk <achaulk@chromium.org>
Tested-by: Albert Chaulk <achaulk@chromium.org>
(cherry picked from commit 00c4bc52e35c7c77ebe73322693a457b3dd072f9)

Change-Id: I90e6118114554a05245fb8cfcec9567c4705ea96
Reviewed-on: https://gerrit.chromium.org/gerrit/49790
Reviewed-by: Albert Chaulk <achaulk@chromium.org>
Tested-by: Albert Chaulk <achaulk@chromium.org>
Commit-Queue: Albert Chaulk <achaulk@chromium.org>
3 files changed