GLX: Remove all Host_GetRenderWindowSize calls.

Also remove x, y, width and height from the GLInterface, since it's only
used in GLX, which no longer uses them

Source/Core/DolphinWX/GLInterface/GLInterface.h

@@ -104,8 +104,6 @@ typedef struct {
 	XSetWindowAttributes attr;
 	std::thread xEventThread;
 #endif
-	int x, y;
-	unsigned int width, height;
 } GLWindow;
 
 extern GLWindow GLWin;