slub: add 'likely' macro to inc_slabs_node()

After boot phase, 'n' always exist.
So add 'likely' macro for helping compiler.

Acked-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

mm/slub.c

@@ -1005,7 +1005,7 @@ static inline void inc_slabs_node(struct kmem_cache *s, int node, int objects)
 	 * dilemma by deferring the increment of the count during
 	 * bootstrap (see early_kmem_cache_node_alloc).
 	 */
-	if (n) {
+	if (likely(n)) {
 		atomic_long_inc(&n->nr_slabs);
 		atomic_long_add(objects, &n->total_objects);
 	}