MFC r278770, r279114, r279215, r279338, r279543:

MFC r278770, r279114, r279215, r279338, r279543:

  Add logic for handling new-style ARM cpu ID info.

  Correct a comment which was exactly backwards from reality.

  There is no reason to do i+dcache writeback and invalidate when changing
  the translation table (this may be left over from armv5 days).  It's
  especially bad to do so using a cache operation that isn't coherent on
  SMP systems.

  Add casting to make atomic ops work for pointers.  (Apparently nobody has
  ever done atomic ops on pointers before now on arm).

  Revert incorrect casting.

git-svn-id: svn://svn.freebsd.org/base/stable/10@283317 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f