Partial implementation of DMA controller and GPU stubs

src/pse/system.h

@@ -1,6 +1,7 @@
 #pragma once
 #include "bus.h"
 #include "dma.h"
+#include "gpu.h"
 #include "cpu_core.h"
 #include "types.h"
 
@@ -19,4 +20,5 @@ private:
   CPU::Core m_cpu;
   Bus m_bus;
   DMA m_dma;
+  GPU m_gpu;
 };