[mips64] Support for mips n64

Adding remaining mips n64 support including stackwalker.

BUG=None
TEST=manually tested on Linux/Android
R=vapier@chromium.org

Review URL: https://codereview.chromium.org/1418453011 .

src/processor/stackwalk_common.cc

@@ -546,7 +546,7 @@ static void PrintStack(const CallStack *stack,
         sequence =
             PrintRegister64("pc", frame_arm64->context.iregs[32], sequence);
       }
-    } else if (cpu == "mips") {
+    } else if ((cpu == "mips") || (cpu == "mips64")) {
       const StackFrameMIPS* frame_mips =
         reinterpret_cast<const StackFrameMIPS*>(frame);