[llvm] [SystemZ][z/OS] Add AMODE to PR symbols (PR #223541)

[Kai Nacke via llvm-commits]

redstar wrote:

It seems that the binder considers the AMODE field when resolving symbols, otherwise the setting has no influence.
With this the setting of the AMODE field becomes:

- `ESD_AMODE_None` when the symbol is not used for resolution against references in other compilation units (aka the binding is `Section`), and
- `ESD_AMODE_64` when the symbol take potential part in symbol resolution with symbols from other compilation units (aka the binding scope is `Library` or `Export`)

I fixes the instances were the binding scope was `Section` but I set `AMODE_64`, to make it uniform.

https://github.com/llvm/llvm-project/pull/223541