[clang] [Clang][AArch64] Require SVE or SSVE for scalable types. (PR #91356)

[Paul Walker via cfe-commits]

https://github.com/paulwalker-arm commented:

After further discussion I know understand the `__arm_streaming_compatible` keyword has no affect on the target features in play and only tells the compiler not to emit any SM state changing instructions as part of the calling convention.

https://github.com/llvm/llvm-project/pull/91356