bsc: AssignmentState: voice_call -> rtp_stream

Now that CSD is supported, rename the variable. It is true for both
voice calls and for CSD.

Related: OS#4393
Change-Id: Idfd9a102ad172d3aeaa4222a21357cdcd51680df
diff --git a/bsc/BSC_Tests.ttcn b/bsc/BSC_Tests.ttcn
index aa627b7..ecd9953 100644
--- a/bsc/BSC_Tests.ttcn
+++ b/bsc/BSC_Tests.ttcn
@@ -9390,7 +9390,7 @@
 	BSSAP.send(ass_cmd);
 
 	var AssignmentState st := valueof(ts_AssignmentStateInit);
-	st.voice_call := true;
+	st.rtp_stream := true;
 	st.is_assignment := false;
 	alt {
 	[] as_modify(st);
@@ -11154,7 +11154,7 @@
 	ass_cmd.pdu.bssmap.assignmentRequest.codecList := valueof(ts_BSSMAP_IE_CodecList({ts_CodecFR}));
 
 	var AssignmentState st := valueof(ts_AssignmentStateInit);
-	st.voice_call := true;
+	st.rtp_stream := true;
 	st.is_assignment := true;
 
 	var ExpectCriteria mgcpcrit := {