[llvm] [ARM] Set isCheapToSpeculateCtlz as true for hasV5TOps and no Thumb 1 (PR #154848)

[Eli Friedman via llvm-commits]

https://github.com/efriedma-quic approved this pull request.

LGTM

(You could maybe make an argument that we shouldn't speculate ctz without rbit... but it close enough that it probably doesn't matter much either way.)

https://github.com/llvm/llvm-project/pull/154848