Fix gamecube controller presence detection being broken on the official nintendo gamecube adapter.

[EIREXE]

Port of Rosalie241#512

To check if a controller is present, we were only checking if status was not 0, this is incorrect, as apparently bits 4 and 5 are what tell you if it's connected and what kind of controller (wavebird or standard) it is, see https://github.com/dolphin-emu/dolphin/blob/master/Source/Core/InputCommon/GCAdapter.cpp#L862

In the case of my GC adapter, status was set to 0x4 when a controller was not connected.