[clang] [amdgpu-arch] Replace use of HSA with reading sysfs directly (PR #116651)

[Matt Arsenault via cfe-commits]

arsenm wrote:

> I suppose I cannot attest to whether or not the Driver team will modify this interface,

They must never ever do this. It is their fault and problem if this breaks 


https://github.com/llvm/llvm-project/pull/116651