slub: init_kmem_cache_cpus() and put_cpu_partial() can be static

Change-Id: I9a33ef319fec6393f5aca167a2146aeb0e7a2f01
Acked-by: Glauber Costa <glommer@parallels.com>
Acked-by: Christoph Lameter <cl@linux.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>