Add message for touchpad firmware updater use.

This CL adds the boot message for touchpad firmware update.

BUG=b:65180379
TEST=Run `chromeos-boot-alert update_touchpad_firmware`
     and see the message shows up.
CQ-DEPEND=CL:695042, CL:695043

Change-Id: I7344405aa26714e04dfdbff686072b28b235fcd7
Reviewed-on: https://chromium-review.googlesource.com/694762
Commit-Ready: Chih-Yu Huang <akahuang@chromium.org>
Tested-by: Chih-Yu Huang <akahuang@chromium.org>
Reviewed-by: Chih-Yu Huang <akahuang@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
3 files changed