fix doxygen brief in subzero header files

src/IceInstARM32.h

Index: src/IceInstARM32.h
diff --git a/src/IceInstARM32.h b/src/IceInstARM32.h
index 58c0c5ba01daf62536aa4b8eeb9a2428815f73b1..37c03a14875ab55f7f0d09525c693e66d09a898c 100644
--- a/src/IceInstARM32.h
+++ b/src/IceInstARM32.h
@@ -8,9 +8,11 @@
 //===----------------------------------------------------------------------===//
 ///
 /// \file
-/// This file declares the InstARM32 and OperandARM32 classes and their
-/// subclasses. This represents the machine instructions and operands used for
-/// ARM32 code selection.
+/// \brief Declares the InstARM32 and OperandARM32 classes and their
+/// subclasses.
+///
+/// This represents the machine instructions and operands used for ARM32 code
+/// selection.
 ///
 //===----------------------------------------------------------------------===//