[llvm] [VPlan] Simplify select with constant condition (PR #150357)

[Ramkumar Ramachandra via llvm-commits]

https://github.com/artagnon commented:

Seems like a good straight-forward improvement, but I wonder if a nested match `m_Select(m_VPValue(Cond) ...)` and a `match(Cond, m_True())` would be worth it.

https://github.com/llvm/llvm-project/pull/150357