CodeGen: Adapt to change of PHI operand storage

Commit 133435 "Change how PHINodes store their operands" broke Polly. Fix this
breakage by adapting to the changes in the commit.

llvm-svn: 134434

polly/lib/CodeGeneration.cpp

@@ -727,9 +727,6 @@ public:
     PN = Statement->getInductionVariableForDimension(Dimension);
     const Value *V = PN;
 
-    if (PN->getNumOperands() == 2)
-      V = *(PN->use_begin());
-
     if (VectorVMap)
       (*VectorVMap)[vectorDim][V] = RHS;