fix doxygen brief in subzero header files

src/IceTargetLoweringARM32.cpp

Index: src/IceTargetLoweringARM32.cpp
diff --git a/src/IceTargetLoweringARM32.cpp b/src/IceTargetLoweringARM32.cpp
index 64141091a7f3615df5ae3cfe12dcf4457e7b3d90..f1fc6f1849f72bcb930467c8a1e6efb038ceb0dc 100644
--- a/src/IceTargetLoweringARM32.cpp
+++ b/src/IceTargetLoweringARM32.cpp
@@ -8,7 +8,7 @@
 //===----------------------------------------------------------------------===//
 ///
 /// \file
-/// This file implements the TargetLoweringARM32 class, which consists almost
+/// \brief Implements the TargetLoweringARM32 class, which consists almost
 /// entirely of the lowering sequence for each high-level instruction.
 ///
 //===----------------------------------------------------------------------===//