[llvm] [AArch64] Update the scheduling model for Cortex-X1/2/3/4 (PR #118826)

[Jonathan Thackray via llvm-commits]

https://github.com/jthackray approved this pull request.

LGTM, nice. How much extra performance (roughly) does this provide?

https://github.com/llvm/llvm-project/pull/118826