[llvm] [AMDGPU][FixIrreducible][UnifyLoopExits] Support callbr with inline-asm (PR #149308)

[Robert Imschweiler via llvm-commits]

ro-i wrote:

merged, thanks for all the reviews :)
I'll now rebase the other PRs up in the PR stack. But I'll wait at least a couple of days to merge the next one so that there won't be a mess if something needs to be reverted or fixed

https://github.com/llvm/llvm-project/pull/149308