Move some helper methods to DexRegisterLocation.

Test: test-art-host-gtest-stack_map_test
Change-Id: I0abab008159db023d531df69214cd3bb8c0639bd
diff --git a/compiler/debug/elf_debug_loc_writer.h b/compiler/debug/elf_debug_loc_writer.h
index 4009acb..b663291 100644
--- a/compiler/debug/elf_debug_loc_writer.h
+++ b/compiler/debug/elf_debug_loc_writer.h
@@ -149,9 +149,9 @@
     DexRegisterMap dex_register_map = dex_register_maps[stack_map_index];
     DCHECK(!dex_register_map.empty());
     CodeItemDataAccessor accessor(*method_info->dex_file, method_info->code_item);
-    reg_lo = dex_register_map.GetDexRegisterLocation(vreg);
+    reg_lo = dex_register_map[vreg];
     if (is64bitValue) {
-      reg_hi = dex_register_map.GetDexRegisterLocation(vreg + 1);
+      reg_hi = dex_register_map[vreg + 1];
     }
 
     // Add location entry for this address range.