aubinator: Make the iterator store a pointer to structure descriptions.

aubinator: Make the iterator store a pointer to structure descriptions.

When the iterator encounters a structure field, it now looks up the
gen_group for that structure definition and saves a pointer to it.

This lets us drop a lot of ridiculous code in the caller, which looked
at item->value (<struct NAME dword>), strtok'd the structure name back
out, and looked it up itself.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>