mm/slab: fix section mismatch warning

Use the new __init_refok marker to avoid the
section mismatch warning from slab.c

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
diff --git a/mm/slab.c b/mm/slab.c
index 528243e..2e71a32 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2037,7 +2037,7 @@
 	return left_over;
 }
 
-static int setup_cpu_cache(struct kmem_cache *cachep)
+static int __init_refok setup_cpu_cache(struct kmem_cache *cachep)
 {
 	if (g_cpucache_up == FULL)
 		return enable_cpucache(cachep);