[llvm] [AVR] Add AVR MOVW/ADIW/SUBIW disassembly (PR #146360)

[Ben Shi via llvm-commits]

https://github.com/benshi001 requested changes to this pull request.

Please refer to https://github.com/llvm/llvm-project/issues/146451 for my suggestion.

https://github.com/llvm/llvm-project/pull/146360