[llvm] [LV] Fix sub-reduction PHI in vectorized epilogue (PR #182072)

[via llvm-commits]

bgra8 wrote:

Thanks alot for the fix @sdesmalen-arm !
Is there anything else blocking the submit of this fix? As @aeubanks already mentioned this is blocking our internal testing.

https://github.com/llvm/llvm-project/pull/182072