slob: Fix early boot kernel crash

Commit fd3142a59af2012a7c5dc72ec97a4935ff1c5fc6 broke
slob since a piece of a change for a later patch slipped into
it.

Fengguang Wu writes:

  The commit crashes the kernel w/o any dmesg output (the attached one is
  created by the script as a summary for that run). This is very
  reproducible in kvm for the attached config.
Reported-by: NFengguang Wu <fengguang.wu@intel.com>
Signed-off-by: NChristoph Lameter <cl@linux.com>
Signed-off-by: NPekka Enberg <penberg@kernel.org>

mm/slob.c

@@ -518,7 +518,7 @@ struct kmem_cache *__kmem_cache_create(const char *name, size_t size,
 
 	if (c) {
 		c->name = name;
-		c->size = c->object_size;
+		c->size = size;
 		if (flags & SLAB_DESTROY_BY_RCU) {
 			/* leave room for rcu footer at the end of object */
 			c->size += sizeof(struct slob_rcu);