hal: fix for voice + voip call concurrency

-When voice call interrups ongoing voip call, voip call goes
 to hold state and voice call becomes active. During voice call end
 stop_call is not being called because mode is not set to MODE_NORMAL.
 Voip call becomes active and mode is set to MODE_IN_COMMUNICATION
 after voice call end.
-Fix this issue by removing the dependency on MODE_NORMAL to end
 voice call.

Change-Id: I0103f5c6833fb929cb7975f838bc2c5ec4d94313
CRs-Fixed: 633437