[llvm] [AArch64][SME]Check streaming mode when using SME2 instruction in fra… (PR #109680)

[Sander de Smalen via llvm-commits]

sdesmalen-arm wrote:

> Is the revised check correct with __arm_locally_streaming?

It should be, the `isStreaming()` gets its value from `AArch64TargetMachine::getSubtargetImpl` which sets it if either `-force-streaming=true`, or if the function has the (locally) streaming attribute.

It's probably worth adding a test-case though.

https://github.com/llvm/llvm-project/pull/109680