[llvm] [AMDGPU][NFC] Get rid of OPW constants. (PR #139074)

[Ivan Kosarev via llvm-commits]

kosarev wrote:

> This erases the distinction between OPWV216 and OPW32, so I guess nothing actually depended on that distinction?

What `OPWV*` constants were introduced for in 9be7b0d485088e001e13e84b12fbd86c3c92167e is now handled based on operand types. So effectively unused.

https://github.com/llvm/llvm-project/pull/139074