[llvm] [LoongArch] Add processor models la64v1.0 and la64v1.1 (PR #110211)

[WÁNG Xuěruì via llvm-commits]

https://github.com/xen0n commented:

While the changes here are good, I think it may be a good idea to also make the `generic` target to support FP and LSX (but not LASX), as per [the recommended general computing baseline by Loongson](https://github.com/loongson/la-softdev-convention/blob/v0.1/la-softdev-convention.adoc#73-vector-instruction-support). This is tangential to the issue at hand though, and we can do it in a separate PR if you agree. (I'm surprised to realize that `generic` does not support FP but the equally generic-sounding `loongarch64` does -- this is very confusing and I always struggle to remember these details, even to this day.)

https://github.com/llvm/llvm-project/pull/110211