[llvm] [AArch64] Combine subtract with borrow to SBC. (PR #165271)

[Ricardo Jesus via llvm-commits]

rj-jesus wrote:

> question: does adc have this problem too or?

I believe so. I can look into extending this PR with ADC once it lands (or I can do so during review if that's more practical).

https://github.com/llvm/llvm-project/pull/165271