Add helper method to iterate over BitTable fields in CodeInfo.

Avoid the repetitive code patterns and simplify code.

Test: test-art-host-gtest-stack_map_test
Test: checked output of oatdump
Change-Id: I2354bc652837eb34efeecf4de56a027384544034
diff --git a/compiler/optimizing/stack_map_stream.h b/compiler/optimizing/stack_map_stream.h
index df11709..01c6bf9 100644
--- a/compiler/optimizing/stack_map_stream.h
+++ b/compiler/optimizing/stack_map_stream.h
@@ -109,7 +109,7 @@
   BitTableBuilder<RegisterMask> register_masks_;
   BitmapTableBuilder stack_masks_;
   BitmapTableBuilder dex_register_masks_;
-  BitTableBuilder<MaskInfo> dex_register_maps_;
+  BitTableBuilder<DexRegisterMapInfo> dex_register_maps_;
   BitTableBuilder<DexRegisterInfo> dex_register_catalog_;
 
   ScopedArenaVector<BitVector*> lazy_stack_masks_;