audio-hal: Update voice 'in_call' flag

When RIL sends CALL_INACTIVE, the corresponding voice session is closed
and call_state is set to INACTIVE whereas the in_call flag is not reset.
This causes any subsequent voice call usecase to be not setup as in_call
flag is still set as true.

Fix by checking resetting the in_call flag if no other voice session
(in 'dual sim dual active' cases) is active.

Bug: 66873748
Test: make
Change-Id: I109b8badf5a76e68ba64d1c81ce507b62e9e9a5a