engine_interface: Add missing virtual destructor

Eliminates a potential bug vector related to inheritance. Plus, we
should generally be specifying the destructor as virtual within purely
virtual interfaces to begin with.

src/video_core/engines/fermi_2d.h

@@ -35,7 +35,7 @@ namespace Tegra::Engines {
 class Fermi2D final : public EngineInterface {
 public:
     explicit Fermi2D();
-    ~Fermi2D();
+    ~Fermi2D() override;
 
     /// Binds a rasterizer to this engine.
     void BindRasterizer(VideoCore::RasterizerInterface* rasterizer);