[llvm] [SimplfyCFG] Set `MD_prof` for `select` used for certain conditional simplifications (PR #154426)

[Mircea Trofin via llvm-commits]

mtrofin wrote:

That's OK, the `!prof` stuff is only added if the instruction is a `SelectInst` (unless I missed something, at least that's what I think I wrote 😄 )

https://github.com/llvm/llvm-project/pull/154426