GPU: Add Reactive flushing

src/video_core/rasterizer_download_area.h

@@ -0,0 +1,13 @@
+#pragma once
+
+#include "common/common_types.h"
+
+namespace VideoCore {
+
+struct RasterizerDownloadArea {
+    VAddr start_address;
+    VAddr end_address;
+    bool preemtive;
+};
+
+} // namespace VideoCore