Don't query supported sample rates for ASIO devices in PortaudioBackend

There has been reports this can take several minutes on some devices so just
return the default rates(and fail to open the device when a SR is specified
that isn't supported)

libs/backends/portaudio/portaudio_io.cc

@@ -117,6 +117,13 @@ PortAudioIO::available_sample_rates(int device_id, std::vector<float>& sampleRat
 {
 	if (!initialize_pa()) return -1;
 
+#ifdef WITH_ASIO
+	if (get_current_host_api_type() == paASIO) {
+		get_default_sample_rates(sampleRates);
+		return 0;
+	}
+#endif
+
 	// TODO use  separate int device_input, int device_output ?!
 	if (device_id == DeviceDefault) {
 		device_id = get_default_input_device ();