mm: move kmem_cache_init() declaration to mm/slab.h

kmem_cache_init() is called only from mm_core_init(), there is no need to
declare it in include/linux/slab.h

Move kmem_cache_init() declaration to mm/slab.h

Link: https://lkml.kernel.org/r/20230321170513.2401534-13-rppt@kernel.orgSigned-off-by: Mike Rapoport (IBM) <rppt@kernel.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Doug Berger <opendmb@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/slab.h

@@ -167,7 +167,6 @@ struct mem_cgroup;
 /*
  * struct kmem_cache related prototypes
  */
-void __init kmem_cache_init(void);
 bool slab_is_available(void);
 
 struct kmem_cache *kmem_cache_create(const char *name, unsigned int size,

mm/mm_init.c

@@ -27,6 +27,7 @@
 #include <linux/swap.h>
 #include <linux/cma.h>
 #include "internal.h"
+#include "slab.h"
 #include "shuffle.h"
 
 #include <asm/setup.h>

mm/slab.h

@@ -4,6 +4,7 @@
 /*
  * Internal slab definitions
  */
+void __init kmem_cache_init(void);
 
 /* Reuses the bits in struct page */
 struct slab {