[ConstantFold] Don't incorrectly infer inbounds on array GEP

The many levels of nesting inside the responsible code made it easy for
bugs to sneak in.  Flattening the logic makes it easier to see what's
going on.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@275244 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed