[llvm] [LLVM][AARCH64]Replace +sme2p1+smef16f16 by +smef16f16 (PR #88860)

[Tomas Matheson via llvm-commits]

tmatheson-arm wrote:

I think that the dependencies are implemented incorrectly here (and in previous patches). Apparently `FEAT_INIT` indicates that the extension is a non-FMV extension, and the string list of dependencies that follows it is a list of dependencies for FMV. Therefore, historically, extensions with `FEAT_INIT` would always have an empty list of FMV dependencies.

The effect of this is allowing a `-target-feature` to be specified without specifying any of its dependencies on the `-cc1` command line. Every necessary `SubtargetFeature` should be specified explicitly with `-target-feature` and not rely on any dependency resolution at this stage. This means that tests like `clang/test/CodeGen/aarch64-sve2p1-intrinsics/acle_sve2p1_bfclamp.c` are wrong, because they should specify all the `-target-feature` flags that they need.

At least, that's my current understanding.

https://github.com/llvm/llvm-project/pull/88860