TTY: Telephony changes

This CL makes the following changes:
  1. Deleted the tty_enabled config. This config is now
     stored in Telecomm. Telephony stills needs to access
     this value so it now uses TelecommManager to get it.

  2. Deleted the code to set the Phoen's TTY mode based on
     TTY_PREFERRED_MODE_CHANGE_ACTION action. This code is
     now in Telecomm. Telecomm will send a
     ACTION_CURRENT_TTY_MODE_CHANGED action when the devices
     actual TTY mode changes. The actual mode is based on
     the preferred mdoe and the wired headset state.

  3. Added TtyManager which listens for
     ACTION_CURRENT_TTY_MODE_CHANGED and changes the phone's
     TTY state. The old code would update the audio TTY mode
     when the phone's state had finished changing. I've
     moved this code into Telecomm.

Change-Id: I652b095af30cc2732a06829dc23492e5355660da
5 files changed