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/evdev/evdev.h

@@ -8,13 +8,11 @@
 #include <string>
 #include <vector>
 
-#include "InputCommon/ControllerInterface/Device.h"
-
 namespace ciface
 {
 namespace evdev
 {
-void Init(std::vector<Core::Device*>& devices);
+void Init();
 
 class evdevDevice : public Core::Device
 {