Stop casting away const qualifier needlessly.

llvm-svn: 163258
diff --git a/llvm/lib/Target/Mips/MipsISelLowering.cpp b/llvm/lib/Target/Mips/MipsISelLowering.cpp
index 91f91b1..aa7b459 100644
--- a/llvm/lib/Target/Mips/MipsISelLowering.cpp
+++ b/llvm/lib/Target/Mips/MipsISelLowering.cpp
@@ -1571,7 +1571,7 @@
   if (getTargetMachine().getRelocationModel() != Reloc::PIC_ && !IsN64) {
     SDVTList VTs = DAG.getVTList(MVT::i32);
 
-    MipsTargetObjectFile &TLOF = (MipsTargetObjectFile&)getObjFileLowering();
+    const MipsTargetObjectFile &TLOF = (const MipsTargetObjectFile&)getObjFileLowering();
 
     // %gp_rel relocation
     if (TLOF.IsGlobalInSmallSection(GV, getTargetMachine())) {