[llvm] [AArch64] Add flag to control unrolling for small multi-exit loops (PR #131998)

[David Sherwood via llvm-commits]

david-arm wrote:

I've now enabled unrolling of small, multi-exit loops by default for all cores and removed the extra flag I added previously, in favour of the existing `-unroll-runtime-multi-exit`.

https://github.com/llvm/llvm-project/pull/131998