[llvm] [CodeGen, CHERI] Add capability types to MVT. (PR #156616)

[Jessica Clarke via llvm-commits]

jrtc27 wrote:

> > Authorship probably shouldn’t claim to be solely you
> 
> Added co-author lines to the commit message. I thought about adding pointers to the downstream commits in the commit log, but maybe that's overkill?

LLVM is purely "Squash and merge" and configured to use the PR description as the commit message, so please update that.

https://github.com/llvm/llvm-project/pull/156616