[ThinLTO] Address post-review suggestions for index-based WPD summary
[ThinLTO] Address post-review suggestions for index-based WPD summary

Removes a couple of unnecessary and/or redundant checks introduced by
r364960.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@364968 91177308-0d34-0410-b5e6-96231b3b80d8

GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/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,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm