mm/slab: consolidate includes in the internal mm/slab.h

The #include's are scattered at several places of the file, but it does
not seem this is needed to prevent any include loops (anymore?) so
consolidate them at the top. Also move the misplaced kmem_cache_init()
declaration away from the top.
Acked-by: David Rientjes <rientjes@google.com>
Tested-by: David Rientjes <rientjes@google.com>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

mm/slab.h

 /* SPDX-License-Identifier: GPL-2.0 */
 #ifndef MM_SLAB_H
 #define MM_SLAB_H
+
+#include <linux/reciprocal_div.h>
+#include <linux/list_lru.h>
+#include <linux/local_lock.h>
+#include <linux/random.h>
+#include <linux/kobject.h>
+#include <linux/sched/mm.h>
+#include <linux/memcontrol.h>
+#include <linux/fault-inject.h>
+#include <linux/kmemleak.h>
+#include <linux/kfence.h>
+#include <linux/kasan.h>
+
 /*
  * Internal slab definitions
  */
-void __init kmem_cache_init(void);
 
 #ifdef CONFIG_64BIT
 # ifdef system_has_cmpxchg128
@@ -209,11 +221,6 @@ static inline size_t slab_size(const struct slab *slab)
 	return PAGE_SIZE << slab_order(slab);
 }
 
-#include <linux/kfence.h>
-#include <linux/kobject.h>
-#include <linux/reciprocal_div.h>
-#include <linux/local_lock.h>
-
 #ifdef CONFIG_SLUB_CPU_PARTIAL
 #define slub_percpu_partial(c)			((c)->partial)
 
@@ -347,14 +354,6 @@ static inline int objs_per_slab(const struct kmem_cache *cache,
 	return slab->objects;
 }
 
-#include <linux/memcontrol.h>
-#include <linux/fault-inject.h>
-#include <linux/kasan.h>
-#include <linux/kmemleak.h>
-#include <linux/random.h>
-#include <linux/sched/mm.h>
-#include <linux/list_lru.h>
-
 /*
  * State of the slab allocator.
  *
@@ -405,6 +404,7 @@ gfp_t kmalloc_fix_flags(gfp_t flags);
 /* Functions provided by the slab allocators */
 int __kmem_cache_create(struct kmem_cache *, slab_flags_t flags);
 
+void __init kmem_cache_init(void);
 void __init new_kmalloc_cache(int idx, enum kmalloc_cache_type type,
 			      slab_flags_t flags);
 extern void create_boot_cache(struct kmem_cache *, const char *name,