[llvm] [M68k] Add remaining addressing modes for Atomic operations (PR #115523)

[via llvm-commits]

knickish wrote:

> @knickish Can you tell me what changes are necessary for Rust to generate EM_68K binaries?

@ glaubitz I cannot, I am stuck on this also, at least for large enough binaries :(  Have been experimenting with the relocation model linker flags and such, but can't seem to get it working. I will ping you on rust zulip to continue discussing if that works for you

https://github.com/llvm/llvm-project/pull/115523