[DagCombiner] Don't bother adding to the work list if TLI.BuildSDIVPow2 failed. NFCI.
[DagCombiner] Don't bother adding to the work list if TLI.BuildSDIVPow2 failed. NFCI.

Matches the code in BuildSDIV/BuildUDIV

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@339757 91177308-0d34-0410-b5e6-96231b3b80d8

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