With per-cpu partial list, slab is added to partial list first and then moved
to node list. The __slab_free() code path for add/remove_partial is almost
deprecated(except for slub debug). But we forget to account add/remove_partial
when move per-cpu partial pages to node list, so the statistics for such events
are always 0. Add corresponding accounting.

This is against the patch "slub: use correct parameter to add a page to
partial list tail"
Acked-by: NChristoph Lameter <cl@linux.com>
Signed-off-by: NShaohua Li <shaohua.li@intel.com>
Signed-off-by: NPekka Enberg <penberg@kernel.org>