Fix Mips64 utils.h typo

Include of art's utils.h was mistyped as util.h, and instead
brought in external/icu/icu4c/source/common/util.h,
which caused art build failures from -Wdeprecated warnings
when Mips64 libart is compiled with clang.

Change-Id: I9370c4dc041eaecc5d5a1490ec23034ece4322a9
diff --git a/runtime/arch/mips64/context_mips64.cc b/runtime/arch/mips64/context_mips64.cc
index ce99b40..6b3f4c9 100644
--- a/runtime/arch/mips64/context_mips64.cc
+++ b/runtime/arch/mips64/context_mips64.cc
@@ -18,7 +18,7 @@
 
 #include "mirror/art_method-inl.h"
 #include "quick/quick_method_frame_info.h"
-#include "util.h"
+#include "utils.h"
 
 namespace art {
 namespace mips64 {