SLUB: Do not upset lockdep

inconsistent {softirq-on-W} -> {in-softirq-W} usage.
swapper/0 [HC0[0]:SC1[1]:HE0:SE0] takes:
 (&n->list_lock){-+..}, at: [<ffffffff802935c1>] add_partial+0x31/0xa0
{softirq-on-W} state was registered at:
  [<ffffffff80259fb8>] __lock_acquire+0x3e8/0x1140
  [<ffffffff80259838>] debug_check_no_locks_freed+0x188/0x1a0
  [<ffffffff8025ad65>] lock_acquire+0x55/0x70
  [<ffffffff802935c1>] add_partial+0x31/0xa0
  [<ffffffff805c76de>] _spin_lock+0x1e/0x30
  [<ffffffff802935c1>] add_partial+0x31/0xa0
  [<ffffffff80296f9c>] kmem_cache_open+0x1cc/0x330
  [<ffffffff805c7984>] _spin_unlock_irq+0x24/0x30
  [<ffffffff802974f4>] create_kmalloc_cache+0x64/0xf0
  [<ffffffff80295640>] init_alloc_cpu_cpu+0x70/0x90
  [<ffffffff8080ada5>] kmem_cache_init+0x65/0x1d0
  [<ffffffff807f1b4e>] start_kernel+0x23e/0x350
  [<ffffffff807f112d>] _sinittext+0x12d/0x140
  [<ffffffffffffffff>] 0xffffffffffffffff

This change isn't really necessary for correctness, but it prevents lockdep
from getting upset and then disabling itself.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Christoph Lameter <clameter@sgi.com>