fix doxygen brief in subzero header files

src/IceInstX8664.cpp

 //===- subzero/src/IceInstX8664.cpp - X86-64 instruction implementation ---===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
-/// This file defines X8664 specific data related to X8664 Instructions and
-/// Instruction traits. These are declared in the IceTargetLoweringX8664Traits.h
-/// header file.
+/// \brief This file defines X8664 specific data related to X8664 Instructions
+/// and Instruction traits.
+///
+/// These are declared in the IceTargetLoweringX8664Traits.h header file.
 ///
 /// This file also defines X8664 operand specific methods (dump and emit.)
 ///
 //===----------------------------------------------------------------------===//
 #include "IceInstX8664.h"
 
 #include "IceAssemblerX8664.h"
 #include "IceCfg.h"
 #include "IceCfgNode.h"
 #include "IceConditionCodesX8664.h"
@@ skipping 227 matching lines @@
     Var->dump(Func);
   else
     Var->dump(Str);
   Str << ")";
 }
 
 } // namespace X86Internal
 } // end of namespace Ice
 
 X86INSTS_DEFINE_STATIC_DATA(TargetX8664)