[Sparc] Constification of TargetMachine arguments

This patch changes the TargetMachine arguments to be const. This is
required for {D19265}, and was requested to be done in a separate patch.

Patch by Jacob Hansen!

Differential Revision: http://reviews.llvm.org/D19797

llvm-svn: 268389
diff --git a/llvm/lib/Target/Sparc/SparcISelLowering.cpp b/llvm/lib/Target/Sparc/SparcISelLowering.cpp
index 4988c9f..c31e7c5 100644
--- a/llvm/lib/Target/Sparc/SparcISelLowering.cpp
+++ b/llvm/lib/Target/Sparc/SparcISelLowering.cpp
@@ -1448,7 +1448,7 @@
   }
 }
 
-SparcTargetLowering::SparcTargetLowering(TargetMachine &TM,
+SparcTargetLowering::SparcTargetLowering(const TargetMachine &TM,
                                          const SparcSubtarget &STI)
     : TargetLowering(TM), Subtarget(&STI) {
   MVT PtrVT = MVT::getIntegerVT(8 * TM.getPointerSize());