audio-hal: Use call state to ensure voice call start

When RIL goes from CALL_ACTIVE to  CALL_INACTIVE,
voice session would be closed. And call_state is
set to INACTIVE whereas in_call flag is not reset.
This would cause any subsequent voice call usecase
cannot set up as in_call flag already is true.

Fix by checking current call state instead of in_call
flag to start voice call.

Bug: 68969429
Bug: 79266068
Test: manual voice-call test

Change-Id: I2becaf8e539494f783daeb915c62eacbbadabaea