Ignore "no-frame-pointer-elim" and "no-frame-pointer-elim-non-leaf" in favor of "frame-pointer"

D56351 (included in LLVM 8.0.0) introduced "frame-pointer".  All tests
which use "no-frame-pointer-elim" or "no-frame-pointer-elim-non-leaf"
have been migrated to use "frame-pointer".

Implement UpgradeFramePointerAttributes to upgrade the two obsoleted
function attributes for bitcode. Their semantics are ignored.

Differential Revision: https://reviews.llvm.org/D71863