voicecall,common: move call_status_to_string() to common

call_status_to_string() is useful for debug output.
Change signature to contain enum call_status
Replace default case to get compiler warning when new enums added

src/common.c

@@ -743,3 +743,25 @@ void ofono_call_init(struct ofono_call *call)
 	call->cnap_validity = CNAP_VALIDITY_NOT_AVAILABLE;
 	call->clip_validity = CLIP_VALIDITY_NOT_AVAILABLE;
 }
+
+const char *call_status_to_string(enum call_status status)
+{
+	switch (status) {
+	case CALL_STATUS_ACTIVE:
+		return "active";
+	case CALL_STATUS_HELD:
+		return "held";
+	case CALL_STATUS_DIALING:
+		return "dialing";
+	case CALL_STATUS_ALERTING:
+		return "alerting";
+	case CALL_STATUS_INCOMING:
+		return "incoming";
+	case CALL_STATUS_WAITING:
+		return "waiting";
+	case CALL_STATUS_DISCONNECTED:
+		return "disconnected";
+	}
+
+	return "unknown";
+}

src/common.h

@@ -184,3 +184,4 @@ const char *registration_tech_to_string(int tech);
 const char *packet_bearer_to_string(int bearer);
 
 gboolean is_valid_apn(const char *apn);
+const char *call_status_to_string(enum call_status status);

src/voicecall.c

@@ -174,26 +174,6 @@ static const char *disconnect_reason_to_string(enum ofono_disconnect_reason r)
 	}
 }
 
-static const char *call_status_to_string(int status)
-{
-	switch (status) {
-	case CALL_STATUS_ACTIVE:
-		return "active";
-	case CALL_STATUS_HELD:
-		return "held";
-	case CALL_STATUS_DIALING:
-		return "dialing";
-	case CALL_STATUS_ALERTING:
-		return "alerting";
-	case CALL_STATUS_INCOMING:
-		return "incoming";
-	case CALL_STATUS_WAITING:
-		return "waiting";
-	default:
-		return "disconnected";
-	}
-}
-
 static const char *phone_and_clip_to_string(const struct ofono_phone_number *n,
 						int clip_validity)
 {