GekkoDisassembler: Remove unread variable m_sreg

Source/Core/Common/GekkoDisassembler.h

@@ -105,7 +105,6 @@ private:
   static std::string m_opcode;    // Buffer for opcode, min. 10 chars.
   static std::string m_operands;  // Operand buffer, min. 24 chars.
   static unsigned char m_flags;   // Additional flags
-  static unsigned short m_sreg;   // Register in load/store instructions
   static u32 m_displacement;      // Branch- or load/store displacement
 };
 }  // namespace Common