fix doxygen brief in subzero header files

src/IceTargetLoweringMIPS32.cpp

 //===- subzero/src/IceTargetLoweringMIPS32.cpp - MIPS32 lowering ----------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
-/// This file implements the TargetLoweringMIPS32 class, which consists almost
+/// \brief Implements the TargetLoweringMIPS32 class, which consists almost
 /// entirely of the lowering sequence for each high-level instruction.
 ///
 //===----------------------------------------------------------------------===//
 
 #include "IceTargetLoweringMIPS32.h"
 
 #include "IceCfg.h"
 #include "IceCfgNode.h"
 #include "IceClFlags.h"
 #include "IceDefs.h"
@@ skipping 1052 matching lines @@
   Ostream &Str = Ctx->getStrEmit();
   Str << "\t.set\tnomicromips\n";
   Str << "\t.set\tnomips16\n";
 }
 
 llvm::SmallBitVector TargetMIPS32::TypeToRegisterSet[IceType_NUM];
 llvm::SmallBitVector TargetMIPS32::RegisterAliases[RegMIPS32::Reg_NUM];
 llvm::SmallBitVector TargetMIPS32::ScratchRegs;
 
 } // end of namespace Ice