Fix an error in regression test

IsDbusCheckedRegion is used to check whether an memory operation should be checked with the ref Riscv Golden CPU. 
Only IO region should be checked.

src/test/cpp/regression/main.cpp

@@ -3287,7 +3287,7 @@ public:
 	    stdinRestore();
 	    #endif
 	}
-	virtual bool isDBusCheckedRegion(uint32_t address){ return isPerifRegion();}
+	virtual bool isDBusCheckedRegion(uint32_t address){ return isPerifRegion();} // Should only check IO region
 	virtual bool isPerifRegion(uint32_t addr) { return (addr & 0xF0000000) == 0xF0000000 || (addr & 0xE0000000) == 0xE0000000;}
     virtual bool isMmuRegion(uint32_t addr) { return true; }