slab: remove duplicate kmem_cache_init_late() declarations

kmem_cache_init_late() has been declared in slab.h

CC: Nick Piggin <npiggin@suse.de>
CC: Matt Mackall <mpm@selenic.com>
CC: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>

include/linux/slub_def.h

@@ -304,6 +304,4 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
 }
 #endif
 
-void __init kmem_cache_init_late(void);
-
 #endif /* _LINUX_SLUB_DEF_H */