Declare TTY intents to be protected broadcasts

- CURRENT_TTY_MODE_CHANGED and TTY_PREFERRED_MODE_CHANGED are system
  broadcasts that need to protected
- Even though these broadcasts are throwing a non-fatal exception
  and not causing a functionality issue for now, they are likely to
  be treated as errors in later releases

Change-Id: I184cffe4bd9358aa3fab5fcc8c92b55399ec4241
CRs-Fixed: 1030918