ART: Add support for "silvermont" variant

The variant is already supported in the build system and wired up
for the Nexus Player (fugu). The values are copied from the build
system and correspond to documentation in, e.g.,
http://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-optimization-manual.pdf
chapter 15, section 1.1.

Change-Id: I9facaa9d5b8bae3d98cf48f2969d02d11ebfe0e4
diff --git a/runtime/arch/instruction_set_features.h b/runtime/arch/instruction_set_features.h
index e4513ef..d10ae21 100644
--- a/runtime/arch/instruction_set_features.h
+++ b/runtime/arch/instruction_set_features.h
@@ -103,7 +103,7 @@
   explicit InstructionSetFeatures(bool smp) : smp_(smp) {}
 
   // Returns true if variant appears in the array variants.
-  static bool FindVariantInArray(const char* variants[], size_t num_variants,
+  static bool FindVariantInArray(const char* const variants[], size_t num_variants,
                                  const std::string& variant);
 
   // Add architecture specific features in sub-classes.