[NFC][InstCombine] Fixup comments
[NFC][InstCombine] Fixup comments

As noted in post-commit review of rL375378375378.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@375397 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm