[clang] [llvm] [RISCV] Remove experimental from Ztso. (PR #96465)

[Philip Reames via llvm-commits]

preames wrote:

All of the dependent pieces have landed.  For ease of future reference:
* https://github.com/llvm/llvm-project/pull/90266 is the attributes emission (off by default).
* https://github.com/llvm/llvm-project/pull/97347 is the LLD change.
* https://github.com/llvm/llvm-project/pull/87376 is the change to A67 by default

The combination of the first and third mean that the emitted attributes now match our ztso lowering as well.  Unfortunately, most binaries wont have the attributes at all (due to the LD crash on older versions), but that seems unavoidable at this point.  

I have re-landed the original change.

https://github.com/llvm/llvm-project/pull/96465