Merge branch 'work.iov_iter' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull iov_iter infrastructure updates from Al Viro:
 "A couple of iov_iter updates"

* 'work.iov_iter' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  iov_iter: export import_single_range()
  iov_iter: constify {csum_and_,}copy_to_iter()