Clarify which type "Label" refers to (generic vs X86)

src/IceAssemblerMIPS32.h

 //===- subzero/src/IceAssemblerMIPS32.h - Assembler for MIPS ----*- C++ -*-===//
 //
 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 //
 // Modified by the Subzero authors.
 //
 //===----------------------------------------------------------------------===//
 //
@@ skipping 44 matching lines @@
     // TODO(reed kotler) . Find out what this should be.
     static const uint8_t Padding[] = {0xE7, 0xFE, 0xDE, 0xF0};
     return llvm::ArrayRef<uint8_t>(Padding, 4);
   }
 
   void padWithNop(intptr_t Padding) override {
     (void)Padding;
     llvm::report_fatal_error("Not yet implemented.");
   }
 
-  Label *getOrCreateCfgNodeLabel(SizeT NodeNumber) override {
+  Ice::Label *getCfgNodeLabel(SizeT NodeNumber) override {
     (void)NodeNumber;
     llvm_unreachable("Not yet implemented.");
   }
 
   void bindCfgNodeLabel(SizeT NodeNumber) override {
     (void)NodeNumber;
     llvm::report_fatal_error("Not yet implemented.");
   }
 
   bool fixupIsPCRel(FixupKind Kind) const override {
     (void)Kind;
     llvm::report_fatal_error("Not yet implemented.");
   }
 
   static bool classof(const Assembler *Asm) {
     return Asm->getKind() == Asm_MIPS32;
   }
 };
 
 } // end of namespace MIPS32
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICEASSEMBLERMIPS32_H