[llvm] [LVI] Generalize mask not equal conditions handling (PR #92946)

[Antonio Frighetto via llvm-commits]

antoniofrighetto wrote:

> Can you generalize your proofs?

Definitely, updated PR w/ generalized proof (https://alive2.llvm.org/ce/z/dc5BeT).

https://github.com/llvm/llvm-project/pull/92946