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

[Krzysztof Parzyszek via cfe-commits]

kparzysz wrote:

> The address spaces for AMDGPU defined [here](https://github.com/llvm/llvm-project/blob/main/llvm/lib/Target/AMDGPU/AMDGPU.h#L395-L456) contain more types of address spaces in comparison to the enum defined in clang. Is it ok to extend number of address space types for clang?

I'd just move these definitions to their own file, and use that file in clang/flang/llvm backend.  So, indirectly, yes.

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