changes mstatus default value for 64 bits to implement UXL and SXL reads

Author: EAlexJ

src/iss/arch/mstatus.h

@@ -238,7 +238,7 @@ template <typename T> class hart_state<T, typename std::enable_if<std::is_same<T
 
     mstatus_t mstatus;
 
-    static const T mstatus_reset_val = 0x1800;
+    static const T mstatus_reset_val = 0x500001800;
 };
 } // namespace arch
 } // namespace iss