[llvm] [SVE2.1][AArch64] Fix crash for bfadd with scalable vector types (PR #107274)

[Paul Walker via llvm-commits]

paulwalker-arm wrote:

Sorry @vfdff, do you mind if I run with this?  I assigned the bug to myself but forgot to add that after investigation I found many issues.  I've already got a collection of fixes (see https://github.com/llvm/llvm-project/compare/main...paulwalker-arm:llvm-project:sve-bf16-fixes) that I've started converted into PRs.

https://github.com/llvm/llvm-project/pull/107274