mm/slab: remove unused slab_early_init

'slab_early_init' was introduced by 'commit e0a42726
("[PATCH] mm/slab.c: fix early init assumption")', this
flag was used to prevent off-slab caches being created
so early during bootup.

The only user of 'slab_early_init' was removed in 'commit
 3217fd9b ("mm/slab: make criteria for off slab
determination robust and simple")'.
Signed-off-by: Gou Hao <gouhao@uniontech.com>
Acked-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

mm/slab.c

@@ -220,7 +220,6 @@ static inline void fixup_objfreelist_debug(struct kmem_cache *cachep,
 static inline void fixup_slab_list(struct kmem_cache *cachep,
 				struct kmem_cache_node *n, struct slab *slab,
 				void **list);
-static int slab_early_init = 1;
 
 #define INDEX_NODE kmalloc_index(sizeof(struct kmem_cache_node))
 
@@ -1249,8 +1248,6 @@ void __init kmem_cache_init(void)
 	slab_state = PARTIAL_NODE;
 	setup_kmalloc_cache_index_table();
 
-	slab_early_init = 0;
-
 	/* 5) Replace the bootstrap kmem_cache_node */
 	{
 		int nid;