[clang] [compiler-rt] [llvm] [FMV][AArch64] Unify features ssbs and ssbs2. (PR #110297)

[Alexandros Lamprineas via cfe-commits]

labrinea wrote:

Thanks for reviewing! Once this lands it will break the llvm test suite. [This](https://github.com/llvm/llvm-test-suite/pull/168) fixes it.

https://github.com/llvm/llvm-project/pull/110297