[DSE] Fix uninitialized variable (llvm#142768)

Introduced by accident in llvm#138299
(https://lab.llvm.org/buildbot/#/builders/164/builds/10604)

Author: clubby789

llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp

@@ -2029,7 +2029,7 @@ struct DSEState {
     auto *InnerCallee = Malloc->getCalledFunction();
     if (!InnerCallee)
       return false;
-    LibFunc Func;
+    LibFunc Func = NotLibFunc;
     StringRef ZeroedVariantName;
     if (!TLI.getLibFunc(*InnerCallee, Func) || !TLI.has(Func) ||
         Func != LibFunc_malloc) {