[PATCH] mempool: add mempool_create_slab_pool()

Create a simple wrapper function for the common case of creating a slab-based
mempool.

Signed-off-by: Matthew Dobson <colpatch@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>