PowerPC: Disable SLUB for configurations in which slab page structs are modified

PowerPC uses the slab allocator to manage the lowest level of the page
table.  In high cpu configurations we also use the page struct to split the
page table lock.  Disallow the selection of SLUB for that case.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Paul Mackerras <paulus@samba.org>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>