[clang] [AArch64][SME2] Add PEXT, PSEL builtins for SME2 (PR #72827)

[Matthew Devereau via cfe-commits]

================
@@ -1859,19 +1859,28 @@ def SVBGRP   : SInst<"svbgrp[_{d}]",   "ddd", "UcUsUiUl", MergeNone, "aarch64_sv
 def SVBGRP_N : SInst<"svbgrp[_n_{d}]", "dda", "UcUsUiUl", MergeNone, "aarch64_sve_bgrp_x">;
 }
 
+let TargetGuard = "sve2p1|sme" in {
----------------
MDevereau wrote:

```suggestion
let TargetGuard = "sve2p1|sme2" in {
```
Should this be sme2?

https://github.com/llvm/llvm-project/pull/72827