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

[Owen Anderson via llvm-commits]

resistor wrote:

> > Additional note: I've opted to omit the `cAny` tblgen wildcard type from this patch to keep it minimal. I expect to add it in a subsequent patch.
> 
> You mean cPTR?

Sorry, yes. Brain glitch.

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