[clang] [flang] [llvm] [NFC][AMDGPU] Move address space enum to LLVM directory (PR #73944)

[Dominik Adamski via cfe-commits]

DominikAdamski wrote:

@lenary Thank you for your input.
@kparzysz @lenary Shall I add all address spaces which are mentioned in [other LLVM header](https://github.com/llvm/llvm-project/blob/main/llvm/lib/Target/AMDGPU/AMDGPU.h#L395-L456)? Currently I added address spaces which were mentioned in [Clang](https://github.com/llvm/llvm-project/pull/73944/files#diff-06ca78b74b85e093d5b7eddd16b24b4781b2025e6e8bf6c035345155c2649a4d) . 

https://github.com/llvm/llvm-project/pull/73944