ControllerInterface: Don't pass m_devices to the backends

Previously, the devices vector would be passed to all backends. They
would then manually push_back to it to add new devices. This was fine
but caused issues when trying to add synchronisation.

Instead, backends now call AddDevice() to fill m_devices so that it is
not accessible from the outside.

Source/Core/InputCommon/ControllerInterface/OSX/OSX.h

@@ -4,13 +4,11 @@
 
 #pragma once
 
-#include "InputCommon/ControllerInterface/Device.h"
-
 namespace ciface
 {
 namespace OSX
 {
-void Init(std::vector<Core::Device*>& devices, void* window);
+void Init(void* window);
 void DeInit();
 
 void DeviceElementDebugPrint(const void*, void*);