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.

CRs-Fixed: 2130335
Change-Id: Ib449b2ba71b1e998d51df8ae5d2348f651b08751