[clang] [llvm] [AMDGPU] Remove icmp and fcmp intrinsics and builtins (PR #208183)

[Jay Foad via cfe-commits]

jayfoad wrote:

> I think these are still [used by Mesa](https://gitlab.freedesktop.org/mesa/mesa/-/blob/main/src%2Famd%2Fllvm%2Fac_llvm_build.c?ref_type=heads&blame=1#L463) but I don't know how to get those uses fixed, other than landing this so that they are forced to react.

@marekolsak @peppsac FYI

https://github.com/llvm/llvm-project/pull/208183