[clang] [NFC][Clang][AArch64]Refactor implementation of Neon vectors MFloat8… (PR #114804)

[via cfe-commits]

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@@ -201,8 +201,6 @@ SVE_PREDICATE_TYPE_ALL("__clang_svboolx4_t", "svboolx4_t", SveBoolx4, SveBoolx4T
 SVE_OPAQUE_TYPE("__SVCount_t", "__SVCount_t", SveCount, SveCountTy)
 
 AARCH64_VECTOR_TYPE_MFLOAT("__MFloat8_t", "__MFloat8_t", MFloat8, MFloat8Ty, 1, 8, 1)
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SpencerAbson wrote:

```suggestion
AARCH64_VECTOR_TYPE_MFLOAT("__MFloat8_t", "__mfp8", MFloat8, MFloat8Ty, 1, 8, 1)
````

Assuming `u6__mfp8` is the intended mangled name? At the moment it is `u11__MFloat8_t`. We might want to test this in a similar way to `CodeGen/arm-mangle-bf16.cpp`.

It looks to me like the first parameter here should be `__mfp8` too, so we can remove the 
`typedef __MFloat8 __mfp8` in `NeonEmitter` and have this typename defined without the header. Obviously, I may be missing something so ignore me if so!

https://github.com/llvm/llvm-project/pull/114804