mm: slabinfo: remove CONFIG_SLABINFO

According to discussion with Christoph
(https://marc.info/?l=linux-kernel&m=150695909709711&w=2), it sounds like
it is pointless to keep CONFIG_SLABINFO around.

This patch removes the CONFIG_SLABINFO config option, but /proc/slabinfo
is still available.

[yang.s@alibaba-inc.com: v11]
  Link: http://lkml.kernel.org/r/1507656303-103845-3-git-send-email-yang.s@alibaba-inc.com
Link: http://lkml.kernel.org/r/1507152550-46205-3-git-send-email-yang.s@alibaba-inc.com
Signed-off-by: Yang Shi <yang.s@alibaba-inc.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/slub.c b/mm/slub.c
index 1efbb812..025bbb5 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -5852,7 +5852,7 @@
 /*
  * The /proc/slabinfo ABI
  */
-#ifdef CONFIG_SLABINFO
+#ifdef CONFIG_SLUB_DEBUG
 void get_slabinfo(struct kmem_cache *s, struct slabinfo *sinfo)
 {
 	unsigned long nr_slabs = 0;
@@ -5884,4 +5884,4 @@
 {
 	return -EIO;
 }
-#endif /* CONFIG_SLABINFO */
+#endif /* CONFIG_SLUB_DEBUG */