[ScopInfo] Fix typo in method name. NFC.

prependInstrunction -> prependInstruction

Thanks Nandini for noticing.

llvm-svn: 308873
diff --git a/polly/lib/Transform/ForwardOpTree.cpp b/polly/lib/Transform/ForwardOpTree.cpp
index 3ba97a6d..a99b513 100644
--- a/polly/lib/Transform/ForwardOpTree.cpp
+++ b/polly/lib/Transform/ForwardOpTree.cpp
@@ -169,7 +169,7 @@
         // instruction using them.
         // TODO: The operand tree is not really a tree, but a DAG. We should be
         // able to handle DAGs without duplication.
-        TargetStmt->prependInstrunction(Inst);
+        TargetStmt->prependInstruction(Inst);
         NumInstructionsCopied++;
         TotalInstructionsCopied++;
       }