[DAGCombiner] Remove some calls to AddToWorklist that should be unnecessary.
[DAGCombiner] Remove some calls to AddToWorklist that should be unnecessary.

The DAGCombiner has a system for ensuring all nodes are visited. It doesn't require an AddToWorkList for every node that is created by a combine.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@338079 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,apple/swift-llvm,apple/swift-llvm