Fix missing register class.

Adds class name for the "QtoS" register class.

BUG=None
R=eholk@chromium.org

Review URL: https://codereview.chromium.org/1687163002 .
diff --git a/src/IceTargetLoweringARM32.cpp b/src/IceTargetLoweringARM32.cpp
index 2572f7c..f302e35 100644
--- a/src/IceTargetLoweringARM32.cpp
+++ b/src/IceTargetLoweringARM32.cpp
@@ -278,7 +278,9 @@
   default:
     assert(C < RC_Target);
     return regClassString(C);
-    // Add handling of new register classes below.
+  // Add handling of new register classes below.
+  case RegARM32::RCARM32_QtoS:
+    return "QtoS";
   }
 }