[llvm] [AMDGPU] Non convergent readfirstlane does not depend on EXEC. NFCI. (PR #179821)

[Stanislav Mekhanoshin via llvm-commits]

rampitec wrote:

So, my point here is: if it is not convergent, it does not depend on the EXEC. Basically anything, not just this one instruction.

https://github.com/llvm/llvm-project/pull/179821