[llvm] [AArch64] Add scheduling information for flag manipulation instructions in Neoverse-V2 (PR #139765)

[Philipp Rados via llvm-commits]

PhilippRados wrote:

I added the scheduling info for the AXFLAG and XAFLAG instructions. I also changed the instruction matching to not use regex but the instruction definitions directly. From what I've gathered regex is only used when there are multiple very similar instructions that are defined with defm.
One thing I've noticed when trying to remove it was the lingering `def : WriteRes<WriteSys, []> { let Latency = 1; }` on line 1140. This is now mixed in between proper scheduling informations and it might be better to put it somewhere more noticeable. But this is just nit-picking.
Let me know if this is fine like this @Rin18.

https://github.com/llvm/llvm-project/pull/139765