Add TriggerLinkFailure

This new RPC call allows users to trigger link failures. For now only
DisplayPort supports it.

BUG=chromium:963863
TEST=Call Plug then TriggerLinkFailure, the DUT should prune some modes

Change-Id: I8f9b893660abdfad00bb02bc0c844f9c0a57ba71
Reviewed-on: https://chromium-review.googlesource.com/1672366
Tested-by: Simon Ser <contact@emersion.fr>
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Wai-Hong Tam <waihong@google.com>
5 files changed