Doxygenize the documentation comments

src/IceTargetLoweringARM32.cpp

Index: src/IceTargetLoweringARM32.cpp
diff --git a/src/IceTargetLoweringARM32.cpp b/src/IceTargetLoweringARM32.cpp
index 85294b0d4ccd305126228510a5fa9fc6860c0f25..6639da855c97822e11cd531bab1a4b637af61442 100644
--- a/src/IceTargetLoweringARM32.cpp
+++ b/src/IceTargetLoweringARM32.cpp
@@ -6,10 +6,11 @@
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
-//
-// This file implements the TargetLoweringARM32 class, which consists almost
-// entirely of the lowering sequence for each high-level instruction.
-//
+///
+/// \file
+/// This file implements the TargetLoweringARM32 class, which consists almost
+/// entirely of the lowering sequence for each high-level instruction.
+///
 //===----------------------------------------------------------------------===//
 
 #include "IceTargetLoweringARM32.h"