[llvm] [AArch64] Add Ampere1B scheduling/pipeline model (PR #81338)

[Philipp Tomsich via llvm-commits]

ptomsich wrote:

> Er, the build appears to have failed, but you have merged?

The build looked ok on my checkout.  I am rebuilding again to confirm once more.

https://github.com/llvm/llvm-project/pull/81338