Ignore TV platforms in checkForRingerModeChange

The checkForRingerModeChange function determines how to modify the
ringer mode based on the requested action and then calls setRingerMode
to carry out the change. For TV devices, setRingerMode exits
immediately, making the path through checkForRingerModeChange
unnecessary.

Removed all references to TV inside checkForRingerModeChange and
return immediately in that situation.

b/26016241

Change-Id: I15893d38c8b7b449e5a3f1d729f75505a08976a2