Telephony: Add DORMANT state to GSM data link activity

GsmDataConnectionTracker sets its activity flag to DORMANT and notifies
LinkActivity when RIL indicates that all its data calls are in
dormant state (i.e. active is set to 1 in UNSOL_DATA_CALL_LIST_CHANGED
message for all data calls)

CRs-Fixed: 332606
(cherry picked from commit 6b57c3b68d989d6b8f114c5f87dac6fc2c13a5f5)

Change-Id: I1d4b9fd24c4049a938d62f08b7720d47400ad7e1