[llvm] [AArch64][PAC] Refine authenticated pointer check methods (PR #74074)

[Anatoly Trosinenko via llvm-commits]

atrosinenko wrote:

Thank you for the review!

> I'm assuming that aligning the values of the brk operand with what arm64e does helps reduce possible incompatibilities with any users/tools that might interpret these brk operand values?

Yes, the reason was merely to not diverge unless needed.

https://github.com/llvm/llvm-project/pull/74074