fix doxygen brief in subzero header files

src/IceTargetLoweringARM32.h

 //===- subzero/src/IceTargetLoweringARM32.h - ARM32 lowering ----*- 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 TargetLoweringARM32 class, which implements the
+/// \brief Declares the TargetLoweringARM32 class, which implements the
 /// TargetLowering interface for the ARM 32-bit architecture.
 ///
 //===----------------------------------------------------------------------===//
 
 #ifndef SUBZERO_SRC_ICETARGETLOWERINGARM32_H
 #define SUBZERO_SRC_ICETARGETLOWERINGARM32_H
 
 #include "IceDefs.h"
 #include "IceInstARM32.h"
 #include "IceRegistersARM32.h"
@@ skipping 1022 matching lines @@
 
 private:
   ~TargetHeaderARM32() = default;
 
   TargetARM32Features CPUFeatures;
 };
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICETARGETLOWERINGARM32_H