fix doxygen brief in subzero header files

src/IceTargetLoweringMIPS32.cpp

Index: src/IceTargetLoweringMIPS32.cpp
diff --git a/src/IceTargetLoweringMIPS32.cpp b/src/IceTargetLoweringMIPS32.cpp
index 9f1aea6bef097d4442b578ee7bc9dcc11dc7c266..7ce803b4522bf176be6f757dbe11dfb7f91f57c3 100644
--- a/src/IceTargetLoweringMIPS32.cpp
+++ b/src/IceTargetLoweringMIPS32.cpp
@@ -8,7 +8,7 @@
 //===----------------------------------------------------------------------===//
 ///
 /// \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.
 ///
 //===----------------------------------------------------------------------===//