Fix stretching with Virtual XFB in D3D

This change matches the behaviour of OpenGL.

This should make Ty the Tasmanian Tiger 3 stretch across the whole
screen. There are other games with this same issue but I have not any.

See issue #6750 for details

Source/Core/VideoBackends/D3D/Render.cpp

@@ -766,6 +766,8 @@ void Renderer::SwapImpl(u32 xfbAddr, u32 fbWidth, u32 fbStride, u32 fbHeight, co
 			sourceRc.right = (int)xfbSource->texWidth;
 			sourceRc.bottom = (int)xfbSource->texHeight;
 
+			sourceRc.right -= fbStride - fbWidth;
+
 			BlitScreen(sourceRc, drawRc, xfbSource->tex, xfbSource->texWidth, xfbSource->texHeight, Gamma);
 		}
 	}