[clang] [AArch64] Add MSVC mangling for the __mfp8 type (PR #124968)

[Benjamin Maxwell via cfe-commits]

================
@@ -2808,6 +2812,7 @@ void MicrosoftCXXNameMangler::mangleType(const BuiltinType *T, Qualifiers,
 
 #define SVE_TYPE(Name, Id, SingletonId) \
   case BuiltinType::Id:
+#define SVE_SCALAR_TYPE(Name, MangledName, Id, SingletonId, Bits)
----------------
MacDue wrote:

You could define the macro to check the builtin-type is the one you expect (I think `BuiltinType::MFloat8` is the only SVE_SCALAR_TYPE right now). 
```
#define SVE_SCALAR_TYPE(Name, MangledName, Id, SingletonId, Bits)  \
    case BuiltinType::Id:                                          \
      if (BuiltinType::Id == BuiltinType::MFloat8) {                  \
        mangleArtificialTagType(TagTypeKind::Struct, MangledName);   \
        break;                                                                                            \
      }                                                                                                         \
      [[fallthrough]];
```

https://github.com/llvm/llvm-project/pull/124968