Fixed TTY Mode RIL update bug

A recent fix caused a regression where the setTTYMode
RIL command wasn't being sent when TTY was turned on.
This was due to the Phone#setTTYMode method being
overridden in GsmCdmaPhone and not ever being called.

Test: Manual, looked at logs
Bug: 65287215
Change-Id: I5de32c74d4124a2ded37868e5594ab48d92f35ee