[llvm] Add support for ref.func to AsmParser/MC (PR #163326)

[Demetrius Kanios via llvm-commits]

QuantumSegfault wrote:

Alright!

Could you merge this one in, so I can get started on the IR side.

Or would you prefer me augment this PR with the whole thing.

https://github.com/llvm/llvm-project/pull/163326