[llvm] [NFC][ARM] Split SIMD identifier away from MVE (PR #130296)

[Jonathan Thackray via llvm-commits]

jthackray wrote:

So this only affects cortex-m52, cortex-m55 and cortex-m85? Is it worth noting these cores in the change description? I assume there are no other test cases that require updating?

https://github.com/llvm/llvm-project/pull/130296