Avoid unnecessarily casting away const, fixing a FIXME.

llvm-svn: 46591
diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index 21e1944..e29b2db 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -508,7 +508,7 @@
 /// canConstantFoldCallTo - Return true if its even possible to fold a call to
 /// the specified function.
 bool
-llvm::canConstantFoldCallTo(Function *F) {
+llvm::canConstantFoldCallTo(const Function *F) {
   switch (F->getIntrinsicID()) {
   case Intrinsic::sqrt:
   case Intrinsic::powi: