dram simulator fix

sim/simx/constants.h

@@ -1,10 +1,16 @@
 #pragma once
 
-#include "types.h"
-
+#ifndef RAM_PAGE_SIZE
 #define RAM_PAGE_SIZE 4096
+#endif
 
-#define DRAM_CHANNELS 2
+#ifndef MEM_CYCLE_RATIO
+#define MEM_CYCLE_RATIO -1
+#endif
+
+#ifndef MEMORY_BANKS
+#define MEMORY_BANKS 2
+#endif
 
 namespace vortex {