SLUB Debug: Fix object size calculation

The object size calculation is wrong if !CONFIG_SLUB_DEBUG because the
#ifdef CONFIG_SLUB_DEBUG is now switching off the size adjustments for
DESTROY_BY_RCU and ctor.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Acked-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>