9273 loader.efi: We can't use d_opendata for blkio storage.
Review Request #950 - Created March 13, 2018 and submitted
https://svnweb.freebsd.org/base?view=revision&revision=330807 open_disk uses d_opendata for it's own purpse. We can't store blkio there. Fortunately, blkio is stored elsewhere and we never actually retrieve blkio from d_opendata. Eliminate it as a source of confusion. Eliminate all stores of d_opendata in efi since this layer doesn't own that field.