[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.h b/llvm/lib/Target/Sparc/SparcISelLowering.h
index 42a71d8..8716644 100644
--- a/llvm/lib/Target/Sparc/SparcISelLowering.h
+++ b/llvm/lib/Target/Sparc/SparcISelLowering.h
@@ -54,7 +54,7 @@
   class SparcTargetLowering : public TargetLowering {
     const SparcSubtarget *Subtarget;
   public:
-    SparcTargetLowering(TargetMachine &TM, const SparcSubtarget &STI);
+    SparcTargetLowering(const TargetMachine &TM, const SparcSubtarget &STI);
     SDValue LowerOperation(SDValue Op, SelectionDAG &DAG) const override;
 
     /// computeKnownBitsForTargetNode - Determine which of the bits specified