nfs: fix wrong object type in lockowner_slab

commit 3c40794b2dd0f355ef4e6bf8d85af5dcd7da7ece upstream.

The object type in the cache of lockowner_slab is wrong, and it is
better to fix it.

Signed-off-by: Yanchuan Nian <ycnian@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>