MIPS32: Fix codegen register dumps.

Dump raw registers instead of managed registers to be
in line with other architectures. This fixes a checker
failure in 510-checker-try-catch where we have previously
emitted a space that stopped the regexp search. However,
there still remains a runtime failure of the 510 test:
  Exception in thread "main" java.lang.Error:
    Method: "testCatchPhi_double",
    path: ExceptionalFlow1, expected: 3, actual: 0

Change-Id: Ib9ad2c60baf2e322ce1eb58b9dc39feb5ab6f148
diff --git a/compiler/optimizing/code_generator_mips.cc b/compiler/optimizing/code_generator_mips.cc
index fa119bb..f92a68f 100644
--- a/compiler/optimizing/code_generator_mips.cc
+++ b/compiler/optimizing/code_generator_mips.cc
@@ -1132,11 +1132,11 @@
 }
 
 void CodeGeneratorMIPS::DumpCoreRegister(std::ostream& stream, int reg) const {
-  stream << MipsManagedRegister::FromCoreRegister(Register(reg));
+  stream << Register(reg);
 }
 
 void CodeGeneratorMIPS::DumpFloatingPointRegister(std::ostream& stream, int reg) const {
-  stream << MipsManagedRegister::FromFRegister(FRegister(reg));
+  stream << FRegister(reg);
 }
 
 void CodeGeneratorMIPS::InvokeRuntime(QuickEntrypointEnum entrypoint,