fix doxygen brief in subzero header files

src/IceRegistersMIPS32.h

 //===- subzero/src/IceRegistersMIPS32.h - Register information --*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
-/// This file declares the registers and their encodings for MIPS32.
+/// \brief Declares the registers and their encodings for MIPS32.
 ///
 //===----------------------------------------------------------------------===//
 
 #ifndef SUBZERO_SRC_ICEREGISTERSMIPS32_H
 #define SUBZERO_SRC_ICEREGISTERSMIPS32_H
 
 #include "IceDefs.h"
 #include "IceInstMIPS32.def"
 #include "IceOperand.h" // RC_Target
 #include "IceTypes.h"
@@ skipping 37 matching lines @@
 }
 
 } // end of namespace RegMIPS32
 
 // Extend enum RegClass with MIPS32-specific register classes (if any).
 enum RegClassMIPS32 : uint8_t { RCMIPS32_NUM = RC_Target };
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICEREGISTERSMIPS32_H