slab: convert slab_is_available() to boolean

A good candidate to return a boolean result.
Signed-off-by: Denis Kirjanov <kda@linux-powerpc.org>
Cc: Christoph Lameter <cl@linux.com>
Reviewed-by: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/slab.h

@@ -111,7 +111,7 @@ struct mem_cgroup;
  * struct kmem_cache related prototypes
  */
 void __init kmem_cache_init(void);
-int slab_is_available(void);
+bool slab_is_available(void);
 
 struct kmem_cache *kmem_cache_create(const char *, size_t, size_t,
 			unsigned long,

mm/slab_common.c

@@ -692,7 +692,7 @@ int kmem_cache_shrink(struct kmem_cache *cachep)
 }
 EXPORT_SYMBOL(kmem_cache_shrink);
 
-int slab_is_available(void)
+bool slab_is_available(void)
 {
 	return slab_state >= UP;
 }