quectel: Try to update voltage only, when received "vbatt"

As there are some more sources of +QIND: activated, do now only update
voltage when we get the
+QIND: "vbatt",-1
but not on things like
+QIND: "act","LTE"
or
+QIND: "csq",20,99

plugins/quectel.c

@@ -425,10 +425,12 @@ static void qind_notify(GAtResult *result, void *user_data)
 	if (!g_at_result_iter_next_string(&iter, &type))
 		return;
 
-	if (!g_at_result_iter_next_number(&iter, &event))
-		return;
+	if (g_strcmp0("vbatt", type)) {
+		if (!g_at_result_iter_next_number(&iter, &event))
+			return;
 
-	voltage_handle(hw->modem, event);
+		voltage_handle(hw->modem, event);
+	}
 }
 
 static void power_notify(GAtResult *result, void *user_data)