[llvm] [LoopVectorize] Enable more early exit vectorisation tests (PR #117008)

[Paul Walker via llvm-commits]

https://github.com/paulwalker-arm approved this pull request.

This works for me.  Without looking deeper I cannot confirm if #120260 is valid but I figure there's no harm in landing all the fixes (and tests) in this PR and then #120260 can remove the one it improves upon when ready.

https://github.com/llvm/llvm-project/pull/117008