amd/rtld: update the ELF representation of LDS symbols

amd/rtld: update the ELF representation of LDS symbols

The initial prototype used a processor-specific symbol type, but
feedback suggests that an approach using processor-specific section
name that encodes the alignment analogous to SHN_COMMON symbols is
preferred.

This patch keeps both variants around for now to reduce problems
with LLVM compatibility as we switch branches around.

This also cleans up the error reporting in this function.

Tested-by: Dieter Nützel <Dieter@nuetzel-hh.de>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>