Make this code 65-bit clean.

llvm-svn: 114828
diff --git a/llvm/lib/VMCore/Instructions.cpp b/llvm/lib/VMCore/Instructions.cpp
index 401802e..7f8df58 100644
--- a/llvm/lib/VMCore/Instructions.cpp
+++ b/llvm/lib/VMCore/Instructions.cpp
@@ -899,7 +899,7 @@
 
 bool AllocaInst::isArrayAllocation() const {
   if (ConstantInt *CI = dyn_cast<ConstantInt>(getOperand(0)))
-    return CI->getZExtValue() != 1;
+    return !CI->isOne();
   return true;
 }