aubinator: Track the current field's starting dword offset.

aubinator: Track the current field's starting dword offset.

The iterator code already computed this value, then we stored it in
the structure name, strtok'd it back out, and also manually computed
it when printing dword headers.

Just put the value in the struct and use it.  Way simpler.

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