mm: SLOB fix reclaim_state

SLOB does not correctly account reclaim_state.reclaimed_slab, so it will
break memory reclaim. Account it like SLAB does.

Cc: stable@kernel.org
Cc: linux-mm@kvack.org
Acked-by: Matt Mackall <mpm@selenic.com>
Acked-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>