telephony: support for RIL that does not send UNSOL_CALL_RING

Samsung Broadcom RIL does not send UNSOL_CALL_RING at all, so it
needs to be faked or non loop (e.g. Digital Phone) ringtones
won't work.

Change-Id: Ib7373d32777f6c42ee488972a7aa63ae8e1cd09b
telephony: HACK: fix call waiting audio on Dual-SIM

Change-Id: I9978f97cf893512fcce05458d8e5da170aae3fee