Don't assume multiple RING events from the radio layer

Qualcomm radios appear to never send anything beyond RIL_UNSOL_CALL_RING,
so set call_ring.multiple to false

Fixes non-repeating ringtones.
Fixes CYAN-2277

Change-Id: I72680c7585b4a3d0ee0fb85733a9784a87ef4471

Conflicts:
	qcom-common.mk