arch: TheISA shouldn't really ever be used in the arch directory.

We should always refer to the specific ISA in that arch directory.
This is especially necessary if we're ever going to make it to the
point where we actually have heterogeneous systems.

src/arch/mips/stacktrace.hh

@@ -61,7 +61,7 @@ class ProcessInfo
 class StackTrace
 {
   protected:
-    typedef TheISA::MachInst MachInst;
+    typedef MipsISA::MachInst MachInst;
   private:
     ThreadContext *tc;
     std::vector<Addr> stack;