gitadora: show LEFT / RIGHT screens on sub screen in landscape mode (#900)

## Link to GitHub Issue or related Pull Request, if one exists
Continues #899 

## Description of change
#899 added the ability to display the gitadora subscreen in lanscape
mode with black bars on the side. With the new option the black bars can
instead display the LEFT / RIGHT screens, completing the two-monitor
full screen use case for arena model.

## Testing

src/spice2x/hooks/graphics/backends/d3d9/d3d9_device.cpp

@@ -670,7 +670,7 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3DDevice9::Present(
     // an adapter group device presents every head at once, so the SMALL head has to be
     // composed here as well as in its own swap chain
     if (gfdm_small_head.scaled()) {
-        gfdm_small_head.compose(pReal);
+        gfdm_small_head.compose(this);
     }
 
     CHECK_RESULT(pReal->Present(pSourceRect, pDestRect, hDestWindowOverride, pDirtyRegion));