[clang] [Clang][AArch64] Add fp8 variants for untyped NEON intrinsics (PR #128019)

[Paul Walker via cfe-commits]

paulwalker-arm wrote:

For my education can you explain why the fp8 variants are broken out into their own definitions.  Taking `VREV64_MF8` as an example, it looks like you should be able to add the new type strings to the current definition?

https://github.com/llvm/llvm-project/pull/128019