TIF: Add a way to enable/disable caption

This is required to handle the case that an application wants to turn
on/off the caption explicitly (e.g. TvView in PIP). TV input service
implementation must respond to the request immediately to avoid any
legal implication since the captioning is imposed by the law in many
countries.

Bug: 14121898
Change-Id: I9600debae709fdc99065d7a0138ae69d1dffc9ba