[MemorySSA] Reflow comments + clean up control flow; NFC

Style guide says `else`s after returns are iffy, and I agree. I also
don't know what broke the comments here and in CFLAA, but *shrug*.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@333332 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed