[llvm] [M68k] Fix register class of index operands (PR #156146)

[Sergei Barannikov via llvm-commits]

s-barannikov wrote:

And I'm probably wrong as I found this in the manual:
<img width="576" height="92" alt="image" src="https://github.com/user-attachments/assets/4e2ccd1c-d3d5-482a-8504-b8ee615f187e" />

The issue I'm observing must be something else. Marking for draft for now.


https://github.com/llvm/llvm-project/pull/156146