MFC r274407

  Fix incorrect reading of 32-bit modinfo by 64-bit loaders.

  The various structures in the mod_metadata set of a FreeBSD kernel and
  modules contain pointers. The FreeBSD loader correctly deals with a
  mismatch in loader and kernel pointer size (e.g. 32-bit i386/ppc
  loader, loading 64-bit amd64/ppc64 kernels), but wasn't dealing with
  the inverse case where a 64-bit loader was loading a 32-bit kernel.