[lld] [libc][libm][GPU] Add missing vendor entrypoints to the GPU version of `libm` (PR #66034)

[Anton Rydahl via llvm-commits]

AntonRydahl wrote:

> LG after fixing the header formatting.

Thanks a bunch! I don't know how I did not notice the misformatted headers. I have fixed those now.

https://github.com/llvm/llvm-project/pull/66034