[llvm] [AArch64][CostModel] Alter sdiv/srem cost where the divisor is constant (PR #123552)

[David Green via llvm-commits]

davemgreen wrote:

@sushgokh Now that 122469 is in, this should be able to test sve costs correctly if you can give it a rebase. We can hopefully move this forward.

https://github.com/llvm/llvm-project/pull/123552