structured_control_flow: Conditionally invoke demote reorder pass

This is only needed on select drivers when a fragment shader discards/demotes.

src/video_core/renderer_opengl/gl_device.h

@@ -156,6 +156,10 @@ public:
         return shader_backend;
     }
 
+    bool IsAmd() const {
+        return vendor_name == "ATI Technologies Inc.";
+    }
+
 private:
     static bool TestVariableAoffi();
     static bool TestPreciseBug();

src/video_core/renderer_opengl/gl_shader_cache.cpp

@@ -219,6 +219,7 @@ ShaderCache::ShaderCache(RasterizerOpenGL& rasterizer_, Core::Frontend::EmuWindo
       host_info{
           .support_float16 = false,
           .support_int64 = device.HasShaderInt64(),
+          .needs_demote_reorder = device.IsAmd(),
       } {
     if (use_asynchronous_shaders) {
         workers = CreateWorkers();