win-wasapi: Mark GetWASAPIAudioDevices_ as static

plugins/win-wasapi/enum-wasapi.cpp

@@ -36,7 +36,7 @@ string GetDeviceName(IMMDevice *device)
 	return device_name;
 }
 
-void GetWASAPIAudioDevices_(vector<AudioDeviceInfo> &devices, bool input)
+static void GetWASAPIAudioDevices_(vector<AudioDeviceInfo> &devices, bool input)
 {
 	ComPtr<IMMDeviceEnumerator> enumerator;
 	ComPtr<IMMDeviceCollection> collection;