MIPS: Use PCNT to implement VisitIntegerBitCount() and VisitLongBitCount()

Test: ./testrunner.py --target --optimizing in QEMU
Test: mma test-art-host-gtest
Change-Id: I6ce5bdc86f951094f656c2f81ae8fc836d7a0b5c
diff --git a/compiler/optimizing/intrinsics_mips64.h b/compiler/optimizing/intrinsics_mips64.h
index 6f40d90..748b0b0 100644
--- a/compiler/optimizing/intrinsics_mips64.h
+++ b/compiler/optimizing/intrinsics_mips64.h
@@ -68,6 +68,8 @@
 #undef INTRINSICS_LIST
 #undef OPTIMIZING_INTRINSICS
 
+  bool HasMsa() const;
+
  private:
   Mips64Assembler* GetAssembler();