[llvm] [TableGen] Extend direct lookup to instruction values in generic tables. (PR #80486)

[Jason Eckhardt via llvm-commits]

nvjle wrote:

If one of @wangpc-pp , @nhaehnle , @Paul-C-Anagnostopoulos , or @TNorthover could review this small patch, it would be appreciated (chosen based on recent or past commits in this area-- other suggestions welcome). Thank you.

https://github.com/llvm/llvm-project/pull/80486