[llvm] [MC][AMDGPU] Support .reloc BFD_RELOC_{NONE, 32, 64} (PR #114617)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm approved this pull request.

Follow up could move all the targets to use the def files 

https://github.com/llvm/llvm-project/pull/114617